refactor(api): introduce UserContext schema for API dependency injection

Replace direct User database model imports in API endpoints with UserContext
schema, following the architecture principle that API routes should not import
database models directly.

Changes:
- Create UserContext schema in models/schema/auth.py with from_user() factory
- Update app/api/deps.py to return UserContext from all auth dependencies
- Add _get_user_model() helper for functions needing User model access
- Update 58 API endpoint files to use UserContext instead of User
- Add noqa comments for 4 legitimate edge cases (enums, internal helpers)

Architecture validation: 0 errors (down from 61), 11 warnings remain

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/api/v1/admin/audit.py

@@ -17,7 +17,7 @@ from sqlalchemy.orm import Session
 from app.api.deps import get_current_admin_api
 from app.core.database import get_db
 from app.services.admin_audit_service import admin_audit_service
-from models.database.user import User
+from models.schema.auth import UserContext
 from models.schema.admin import (
     AdminAuditLogFilters,
     AdminAuditLogListResponse,
@@ -38,7 +38,7 @@ def get_audit_logs(
     skip: int = Query(0, ge=0, description="Number of records to skip"),
     limit: int = Query(100, ge=1, le=1000, description="Maximum records to return"),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     Get filtered admin audit logs.
@@ -68,7 +68,7 @@ def get_audit_logs(
 def get_recent_audit_logs(
     limit: int = Query(20, ge=1, le=100),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """Get recent audit logs (last 20 by default)."""
     filters = AdminAuditLogFilters(limit=limit)
@@ -79,7 +79,7 @@ def get_recent_audit_logs(
 def get_my_actions(
     limit: int = Query(50, ge=1, le=100),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """Get audit logs for current admin's actions."""
     return admin_audit_service.get_recent_actions_by_admin(
@@ -93,7 +93,7 @@ def get_actions_by_target(
     target_id: str,
     limit: int = Query(50, ge=1, le=100),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     Get all actions performed on a specific target.