迁移合同费用通用附件

1、删除旧费用附件 API、CRUD、模型和专用前端面板，统一改用通用附件能力。

2、调整合同费用接口为 study_id 语义，并补充合同、凭证、发票等附件类型的权限映射。

3、将合同费用新建和编辑改为抽屉流程，详情页与列表页复用同一编辑组件。

4、补充数据库迁移、附件列表、合同费用抽屉和权限场景测试，覆盖旧权限移除与新流程。

backend/app/schemas/contract_fee.py

@@ -5,12 +5,12 @@ from typing import Optional
 
 from pydantic import BaseModel, ConfigDict, Field
 
+from app.schemas.attachment import AttachmentRead
 from app.schemas.contract_fee_payment import ContractFeePaymentRead
-from app.schemas.fee_attachment import FeeAttachmentRead
 
 
 class ContractFeeCreate(BaseModel):
-    project_id: uuid.UUID
+    study_id: uuid.UUID
     center_id: uuid.UUID
     contract_no: Optional[str] = None
     signed_date: Optional[date] = None
@@ -37,7 +37,7 @@ class ContractFeeUpdate(BaseModel):
 
 class ContractFeeRead(BaseModel):
     id: uuid.UUID
-    project_id: uuid.UUID
+    study_id: uuid.UUID
     center_id: uuid.UUID
     contract_no: Optional[str]
     signed_date: Optional[date]
@@ -66,4 +66,4 @@ class ContractFeeListItem(ContractFeeRead):
 
 class ContractFeeDetail(ContractFeeRead):
     payments: list[ContractFeePaymentRead]
-    attachments: dict[str, list[FeeAttachmentRead]]
+    attachments: dict[str, list[AttachmentRead]]

backend/app/schemas/fee_attachment.py

@@ -1,24 +0,0 @@
-import uuid
-from datetime import datetime
-from typing import Optional
-
-from pydantic import BaseModel, ConfigDict
-
-from app.schemas.user import UserDisplay
-
-
-class FeeAttachmentRead(BaseModel):
-    id: uuid.UUID
-    entity_type: str
-    entity_id: uuid.UUID
-    file_type: str
-    filename: str
-    mime_type: Optional[str]
-    size: int
-    storage_key: Optional[str]
-    url: Optional[str]
-    uploaded_by: Optional[UserDisplay]
-    uploaded_by_id: Optional[uuid.UUID] = None
-    uploaded_at: datetime
-
-    model_config = ConfigDict(from_attributes=True)