feat: harden auth and study workflows

- replace plaintext login and unlock requests with RSA-OAEP/AES-GCM encrypted payloads

- add login challenge replay protection, production RSA key validation, and auth tests

- wire compose to environment-driven dev/prod settings without committing local secrets

- update setup-config smoke scripts and Postman docs for encrypted login

- add visit schedule migrations/tests and update study/subject setup workflows

backend/alembic/versions/20260508_03_add_subject_baseline_date.py

@@ -0,0 +1,26 @@
+"""add subject baseline date
+
+Revision ID: 20260508_03
+Revises: 20260508_02
+Create Date: 2026-05-08 16:35:00.000000
+
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = "20260508_03"
+down_revision: Union[str, None] = "20260508_02"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column("subjects", sa.Column("baseline_date", sa.Date(), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column("subjects", "baseline_date")