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/order_item_exceptions.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.order_item_exception_service import order_item_exception_service
-from models.database.user import User
+from models.schema.auth import UserContext
 from app.modules.orders.schemas import (
     BulkResolveRequest,
     BulkResolveResponse,
@@ -53,7 +53,7 @@ def list_exceptions(
     skip: int = Query(0, ge=0),
     limit: int = Query(50, ge=1, le=200),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     List order item exceptions with filtering and pagination.
@@ -96,7 +96,7 @@ def list_exceptions(
 def get_exception_stats(
     vendor_id: int | None = Query(None, description="Filter by vendor"),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     Get exception statistics.
@@ -116,7 +116,7 @@ def get_exception_stats(
 def get_exception(
     exception_id: int = Path(..., description="Exception ID"),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     Get details of a single exception.
@@ -144,7 +144,7 @@ def resolve_exception(
     exception_id: int = Path(..., description="Exception ID"),
     request: ResolveExceptionRequest = ...,
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     Resolve an exception by assigning a product.
@@ -181,7 +181,7 @@ def ignore_exception(
     exception_id: int = Path(..., description="Exception ID"),
     request: IgnoreExceptionRequest = ...,
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     Mark an exception as ignored.
@@ -222,7 +222,7 @@ def bulk_resolve_by_gtin(
     request: BulkResolveRequest,
     vendor_id: int = Query(..., description="Vendor ID"),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_admin_api),
+    current_admin: UserContext = Depends(get_current_admin_api),
 ):
     """
     Bulk resolve all pending exceptions for a GTIN.