diff --git a/backend/app/api/v1/constants.py b/backend/app/api/v1/constants.py
new file mode 100644
index 00000000..28e7b029
--- /dev/null
+++ b/backend/app/api/v1/constants.py
@@ -0,0 +1,22 @@
+from fastapi import APIRouter, Depends
+
+from app.constants import ae, finance, imp, issue, subject, task
+from app.core.deps import get_current_user
+
+router = APIRouter(tags=["FAQ"], dependencies=[Depends(get_current_user)])
+
+
+@router.get(
+    "/",
+    summary="获取前端常量字典",
+    description="返回各模块状态/类型常量，便于前端一次性加载。",
+)
+async def get_constants():
+    return {
+        "task": {"status": task.TASK_STATUS, "priority": task.TASK_PRIORITY},
+        "subject": {"status": subject.SUBJECT_STATUS, "visit_status": subject.VISIT_STATUS},
+        "ae": {"seriousness": ae.AE_SERIOUSNESS, "severity": ae.AE_SEVERITY, "status": ae.AE_STATUS},
+        "issue": {"category": issue.ISSUE_CATEGORY, "level": issue.ISSUE_LEVEL, "status": issue.ISSUE_STATUS},
+        "finance": {"status": finance.FINANCE_STATUS, "category": finance.FINANCE_CATEGORY},
+        "imp": {"tx_types": imp.IMP_TX_TYPES, "batch_status": imp.IMP_BATCH_STATUS},
+    }
diff --git a/backend/app/api/v1/faq_categories.py b/backend/app/api/v1/faq_categories.py
index b6ee1681..349285c0 100644
--- a/backend/app/api/v1/faq_categories.py
+++ b/backend/app/api/v1/faq_categories.py
@@ -7,7 +7,9 @@ from app.core.deps import get_current_user, get_db_session
 from app.crud import audit as audit_crud
 from app.crud import faq_category as category_crud
 from app.crud import member as member_crud
+from app.schemas.common import PaginatedResponse
 from app.schemas.faq import CategoryCreate, CategoryRead, CategoryUpdate
+from app.utils.pagination import paginate
 
 router = APIRouter()
 
@@ -25,6 +27,8 @@ def _check_permission_for_scope(study_id: uuid.UUID | None, current_user, member
     "/",
     response_model=CategoryRead,
     status_code=status.HTTP_201_CREATED,
+    summary="创建 FAQ 分类",
+    description="创建全局或项目内 FAQ 分类，项目 PM/ADMIN 可用，全局仅 ADMIN。",
 )
 async def create_category(
     payload: CategoryCreate,
@@ -54,7 +58,9 @@ async def create_category(
 
 @router.get(
     "/",
-    response_model=list[CategoryRead],
+    response_model=PaginatedResponse[CategoryRead],
+    summary="FAQ 分类列表",
+    description="返回全局及项目内 FAQ 分类列表，可按 study_id 过滤。",
 )
 async def list_categories(
     study_id: uuid.UUID | None = None,
@@ -68,12 +74,14 @@ async def list_categories(
         if not member and current_user.role != "ADMIN":
             raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Not a study member")
     categories = await category_crud.list_categories(db, study_id, include_global=include_global, is_active=is_active)
-    return [CategoryRead.model_validate(c) for c in categories]
+    return paginate([CategoryRead.model_validate(c) for c in categories], total=len(categories))
 
 
 @router.patch(
     "/{category_id}",
     response_model=CategoryRead,
+    summary="更新 FAQ 分类",
+    description="更新分类名称或启停状态，项目 PM/ADMIN 或全局 ADMIN。",
 )
 async def update_category(
     category_id: uuid.UUID,
diff --git a/backend/app/api/v1/faqs.py b/backend/app/api/v1/faqs.py
index 517f1220..de2922d0 100644
--- a/backend/app/api/v1/faqs.py
+++ b/backend/app/api/v1/faqs.py
@@ -8,7 +8,9 @@ from app.crud import audit as audit_crud
 from app.crud import faq_category as category_crud
 from app.crud import faq_item as faq_crud
 from app.crud import member as member_crud
+from app.schemas.common import PaginatedResponse
 from app.schemas.faq import FaqCreate, FaqRead, FaqUpdate
+from app.utils.pagination import paginate
 
 router = APIRouter()
 
@@ -26,6 +28,8 @@ def _check_write_permission(study_id: uuid.UUID | None, current_user, member_rol
     "/",
     response_model=FaqRead,
     status_code=status.HTTP_201_CREATED,
+    summary="创建 FAQ",
+    description="创建全局或项目内 FAQ，项目 FAQ 需项目 PM/ADMIN 权限。",
 )
 async def create_faq(
     payload: FaqCreate,
@@ -61,7 +65,9 @@ async def create_faq(
 
 @router.get(
     "/",
-    response_model=list[FaqRead],
+    response_model=PaginatedResponse[FaqRead],
+    summary="FAQ 列表",
+    description="返回全局与项目 FAQ，可按关键词、分类过滤。",
 )
 async def list_faqs(
     study_id: uuid.UUID | None = None,
@@ -115,12 +121,14 @@ async def list_faqs(
             if role != "PM":
                 continue
         visible.append(FaqRead.model_validate(it))
-    return visible
+    return paginate(visible, total=len(visible))
 
 
 @router.get(
     "/{item_id}",
     response_model=FaqRead,
+    summary="FAQ 详情",
+    description="获取单条 FAQ，非 PM 不能查看停用 FAQ。",
 )
 async def get_faq(
     item_id: uuid.UUID,
@@ -147,6 +155,8 @@ async def get_faq(
 @router.patch(
     "/{item_id}",
     response_model=FaqRead,
+    summary="更新 FAQ",
+    description="更新 FAQ 内容或启停状态，项目内需 PM/ADMIN 权限。",
 )
 async def update_faq(
     item_id: uuid.UUID,
diff --git a/backend/app/api/v1/router.py b/backend/app/api/v1/router.py
index 97a7dc44..96aca791 100644
--- a/backend/app/api/v1/router.py
+++ b/backend/app/api/v1/router.py
@@ -1,6 +1,6 @@
 from fastapi import APIRouter
 
-from app.api.v1 import auth, users, studies, sites, members, comments, attachments, audit_logs, milestones, tasks, dashboard, subjects, visits, aes, issues, data_queries, verifications, imp_products, imp_batches, imp_inventory, imp_transactions, finance, finance_dashboard, faq_categories, faqs
+from app.api.v1 import auth, users, studies, sites, members, comments, attachments, audit_logs, milestones, tasks, dashboard, subjects, visits, aes, issues, data_queries, verifications, imp_products, imp_batches, imp_inventory, imp_transactions, finance, finance_dashboard, faq_categories, faqs, constants
 
 api_router = APIRouter()
 api_router.include_router(auth.router, prefix="/auth", tags=["auth"])
@@ -28,3 +28,4 @@ api_router.include_router(finance.router, prefix="/studies/{study_id}/finance",
 api_router.include_router(finance_dashboard.router, prefix="/studies/{study_id}/finance", tags=["finance"])
 api_router.include_router(faq_categories.router, prefix="/faqs/categories", tags=["faq-categories"])
 api_router.include_router(faqs.router, prefix="/faqs/items", tags=["faqs"])
+api_router.include_router(constants.router, prefix="/constants", tags=["faq"])
diff --git a/backend/app/api/v1/users.py b/backend/app/api/v1/users.py
index e0b55678..ea19aadd 100644
--- a/backend/app/api/v1/users.py
+++ b/backend/app/api/v1/users.py
@@ -4,21 +4,24 @@ from fastapi import APIRouter, Depends, HTTPException, status
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.deps import get_db_session, require_roles
+from app.schemas.common import PaginatedResponse
 from app.crud import user as user_crud
+from app.utils.pagination import paginate
 from app.schemas.user import UserCreate, UserRead, UserUpdate
 
 router = APIRouter()
 
 
-@router.get("/", response_model=list[UserRead])
+@router.get("/", response_model=PaginatedResponse[UserRead], summary="用户列表", description="仅 ADMIN 可用，支持 skip/limit。")
 async def list_users(
     skip: int = 0,
     limit: int = 100,
     db: AsyncSession = Depends(get_db_session),
     current_user=Depends(require_roles(["ADMIN"])),
-) -> list[UserRead]:
+) -> PaginatedResponse[UserRead]:
     users = await user_crud.list_users(db, skip=skip, limit=limit)
-    return list(users)
+    total_users = await user_crud.list_users(db, skip=0, limit=10_000_000)
+    return paginate(list(users), total=len(total_users))
 
 
 @router.post("/", response_model=UserRead, status_code=status.HTTP_201_CREATED)
diff --git a/backend/app/constants/ae.py b/backend/app/constants/ae.py
new file mode 100644
index 00000000..4e8e888a
--- /dev/null
+++ b/backend/app/constants/ae.py
@@ -0,0 +1,3 @@
+AE_SERIOUSNESS = ["NON_SERIOUS", "SERIOUS"]
+AE_SEVERITY = ["G1", "G2", "G3", "G4", "G5"]
+AE_STATUS = ["NEW", "FOLLOW_UP", "CLOSED"]
diff --git a/backend/app/constants/finance.py b/backend/app/constants/finance.py
new file mode 100644
index 00000000..be96fa69
--- /dev/null
+++ b/backend/app/constants/finance.py
@@ -0,0 +1,2 @@
+FINANCE_STATUS = ["DRAFT", "SUBMITTED", "APPROVED", "REJECTED", "PAID"]
+FINANCE_CATEGORY = ["SITE_FEE", "SUBJECT_STIPEND", "TRAVEL", "OTHER"]
diff --git a/backend/app/constants/imp.py b/backend/app/constants/imp.py
new file mode 100644
index 00000000..d442304c
--- /dev/null
+++ b/backend/app/constants/imp.py
@@ -0,0 +1,10 @@
+IMP_TX_TYPES = [
+    "RECEIPT",
+    "DISPENSE",
+    "RETURN",
+    "RECONCILE",
+    "DESTROY",
+    "TRANSFER_IN",
+    "TRANSFER_OUT",
+]
+IMP_BATCH_STATUS = ["ACTIVE", "QUARANTINED", "EXPIRED", "CLOSED"]
diff --git a/backend/app/constants/issue.py b/backend/app/constants/issue.py
new file mode 100644
index 00000000..10d1e760
--- /dev/null
+++ b/backend/app/constants/issue.py
@@ -0,0 +1,3 @@
+ISSUE_CATEGORY = ["RISK", "ISSUE", "PROTOCOL_DEVIATION"]
+ISSUE_LEVEL = ["LOW", "MEDIUM", "HIGH", "CRITICAL"]
+ISSUE_STATUS = ["OPEN", "MITIGATING", "CLOSED"]
diff --git a/backend/app/constants/subject.py b/backend/app/constants/subject.py
new file mode 100644
index 00000000..7be69108
--- /dev/null
+++ b/backend/app/constants/subject.py
@@ -0,0 +1,2 @@
+SUBJECT_STATUS = ["SCREENING", "ENROLLED", "COMPLETED", "DROPPED"]
+VISIT_STATUS = ["PLANNED", "DONE", "MISSED", "CANCELLED"]
diff --git a/backend/app/constants/task.py b/backend/app/constants/task.py
new file mode 100644
index 00000000..2471f576
--- /dev/null
+++ b/backend/app/constants/task.py
@@ -0,0 +1,2 @@
+TASK_STATUS = ["TODO", "DOING", "DONE", "BLOCKED"]
+TASK_PRIORITY = ["LOW", "MEDIUM", "HIGH"]
diff --git a/backend/app/core/deps.py b/backend/app/core/deps.py
index 69c64aa6..c9d5b475 100644
--- a/backend/app/core/deps.py
+++ b/backend/app/core/deps.py
@@ -5,6 +5,7 @@ from fastapi import Depends, HTTPException, status
 from pydantic import ValidationError
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app.core.exceptions import AppException
 from app.core.security import decode_token, oauth2_scheme
 from app.crud import user as user_crud
 from app.crud import member as member_crud
@@ -75,9 +76,10 @@ def require_study_member():
             return current_user
         membership = await member_crud.get_member(db, study_id, current_user.id)
         if not membership or not membership.is_active:
-            raise HTTPException(
+            raise AppException(
+                code="FORBIDDEN",
+                message="Not a member of this study",
                 status_code=status.HTTP_403_FORBIDDEN,
-                detail="Not a member of this study",
             )
         return current_user
 
@@ -96,9 +98,10 @@ def require_study_roles(roles: Iterable[str]):
             return current_user
         membership = await member_crud.get_member(db, study_id, current_user.id)
         if not membership or not membership.is_active or membership.role_in_study not in roles_set:
-            raise HTTPException(
+            raise AppException(
+                code="FORBIDDEN",
+                message="Insufficient study permissions",
                 status_code=status.HTTP_403_FORBIDDEN,
-                detail="Insufficient study permissions",
             )
         return current_user
 
diff --git a/backend/app/core/exceptions.py b/backend/app/core/exceptions.py
new file mode 100644
index 00000000..98a12b99
--- /dev/null
+++ b/backend/app/core/exceptions.py
@@ -0,0 +1,19 @@
+from fastapi import FastAPI, Request, status
+from fastapi.responses import JSONResponse
+
+
+class AppException(Exception):
+    def __init__(self, code: str, message: str, status_code: int = status.HTTP_400_BAD_REQUEST):
+        self.code = code
+        self.message = message
+        self.status_code = status_code
+        super().__init__(message)
+
+
+def register_exception_handlers(app: FastAPI) -> None:
+    @app.exception_handler(AppException)
+    async def app_exception_handler(_: Request, exc: AppException) -> JSONResponse:
+        return JSONResponse(
+            status_code=exc.status_code,
+            content={"code": exc.code, "message": exc.message},
+        )
diff --git a/backend/app/main.py b/backend/app/main.py
index 72f4d198..5f693507 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -5,6 +5,7 @@ from fastapi.middleware.cors import CORSMiddleware
 
 from app.api.v1.router import api_router
 from app.core.config import settings
+from app.core.exceptions import register_exception_handlers
 from app.crud.user import ensure_admin_exists
 from app.db.base import Base
 from app.db.session import SessionLocal, engine
@@ -25,10 +26,39 @@ async def lifespan(_: FastAPI):
 
 def create_app() -> FastAPI:
     app = FastAPI(
-        title="CTMS API",
+        title="CTMS 后端 API",
+        description="临床试验项目管理系统后端接口文档",
         version="0.1.0",
         debug=settings.ENV == "development",
         lifespan=lifespan,
+        openapi_tags=[
+            {"name": "auth", "description": "认证与登录"},
+            {"name": "users", "description": "用户管理"},
+            {"name": "studies", "description": "项目管理"},
+            {"name": "sites", "description": "中心管理"},
+            {"name": "study-members", "description": "项目成员"},
+            {"name": "comments", "description": "通用评论"},
+            {"name": "attachments", "description": "通用附件"},
+            {"name": "audit-logs", "description": "审计日志"},
+            {"name": "milestones", "description": "里程碑"},
+            {"name": "tasks", "description": "任务"},
+            {"name": "dashboard", "description": "项目总览与统计"},
+            {"name": "subjects", "description": "受试者"},
+            {"name": "visits", "description": "访视"},
+            {"name": "aes", "description": "不良事件"},
+            {"name": "issues", "description": "风险 / 问题"},
+            {"name": "data-queries", "description": "数据问题单"},
+            {"name": "verifications", "description": "SDV/SDR 核查进度"},
+            {"name": "imp-products", "description": "药品产品"},
+            {"name": "imp-batches", "description": "药品批次"},
+            {"name": "imp-inventory", "description": "药品库存"},
+            {"name": "imp-transactions", "description": "药品台账流水"},
+            {"name": "finance", "description": "费用管理"},
+            {"name": "faq-categories", "description": "FAQ 分类"},
+            {"name": "faqs", "description": "FAQ 条目"},
+            {"name": "health", "description": "健康检查"},
+            {"name": "faq", "description": "常量字典"},
+        ],
     )
 
     app.add_middleware(
@@ -38,8 +68,14 @@ def create_app() -> FastAPI:
         allow_methods=["*"],
         allow_headers=["*"],
     )
+    register_exception_handlers(app)
 
-    @app.get("/health", tags=["health"])
+    @app.get(
+        "/health",
+        tags=["health"],
+        summary="健康检查",
+        description="返回服务存活状态。",
+    )
     async def health() -> dict[str, str]:
         return {"status": "ok"}
 
diff --git a/backend/app/schemas/common.py b/backend/app/schemas/common.py
new file mode 100644
index 00000000..299734c5
--- /dev/null
+++ b/backend/app/schemas/common.py
@@ -0,0 +1,16 @@
+from typing import Generic, TypeVar
+
+from pydantic import BaseModel
+from pydantic.generics import GenericModel
+
+T = TypeVar("T")
+
+
+class PaginatedResponse(GenericModel, Generic[T]):
+    items: list[T]
+    total: int
+
+
+class MessageResponse(BaseModel):
+    code: str
+    message: str
diff --git a/backend/app/utils/pagination.py b/backend/app/utils/pagination.py
new file mode 100644
index 00000000..cfa06266
--- /dev/null
+++ b/backend/app/utils/pagination.py
@@ -0,0 +1,7 @@
+from collections.abc import Iterable
+from typing import Any
+
+
+def paginate(items: Iterable[Any], total: int | None = None) -> dict[str, Any]:
+    items_list = list(items)
+    return {"items": items_list, "total": total if total is not None else len(items_list)}
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diff --git a/pg_data/pg_wal/000000010000000000000001 b/pg_data/pg_wal/000000010000000000000001
index b3c74466..7307df45 100644
Binary files a/pg_data/pg_wal/000000010000000000000001 and b/pg_data/pg_wal/000000010000000000000001 differ
diff --git a/pg_data/pg_xact/0000 b/pg_data/pg_xact/0000
index 0f749b6f..0f1be393 100644
Binary files a/pg_data/pg_xact/0000 and b/pg_data/pg_xact/0000 differ