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/vendor/invoices.py

@@ -42,7 +42,7 @@ from app.exceptions.invoice import (
 )
 from app.services.invoice_service import invoice_service
 from app.modules.billing.models import FeatureCode
-from models.database.user import User
+from models.schema.auth import UserContext
 from app.modules.orders.schemas import (
     InvoiceCreate,
     InvoiceListPaginatedResponse,
@@ -67,7 +67,7 @@ logger = logging.getLogger(__name__)
 
 @router.get("/settings", response_model=VendorInvoiceSettingsResponse | None)
 def get_invoice_settings(
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
     _: None = Depends(RequireFeature(FeatureCode.INVOICE_LU)),
 ):
@@ -86,7 +86,7 @@ def get_invoice_settings(
 @router.post("/settings", response_model=VendorInvoiceSettingsResponse, status_code=201)
 def create_invoice_settings(
     data: VendorInvoiceSettingsCreate,
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -106,7 +106,7 @@ def create_invoice_settings(
 @router.put("/settings", response_model=VendorInvoiceSettingsResponse)
 def update_invoice_settings(
     data: VendorInvoiceSettingsUpdate,
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -127,7 +127,7 @@ def update_invoice_settings(
 
 @router.get("/stats", response_model=InvoiceStatsResponse)
 def get_invoice_stats(
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -160,7 +160,7 @@ def list_invoices(
     page: int = Query(1, ge=1, description="Page number"),
     per_page: int = Query(20, ge=1, le=100, description="Items per page"),
     status: str | None = Query(None, description="Filter by status"),
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -207,7 +207,7 @@ def list_invoices(
 @router.get("/{invoice_id}", response_model=InvoiceResponse)
 def get_invoice(
     invoice_id: int,
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -224,7 +224,7 @@ def get_invoice(
 @router.post("", response_model=InvoiceResponse, status_code=201)
 def create_invoice(
     data: InvoiceCreate,
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -248,7 +248,7 @@ def create_invoice(
 def update_invoice_status(
     invoice_id: int,
     data: InvoiceStatusUpdate,
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -280,7 +280,7 @@ def update_invoice_status(
 def generate_invoice_pdf(
     invoice_id: int,
     regenerate: bool = Query(False, description="Force regenerate if exists"),
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -301,7 +301,7 @@ def generate_invoice_pdf(
 @router.get("/{invoice_id}/pdf")
 def download_invoice_pdf(
     invoice_id: int,
-    current_user: User = Depends(get_current_vendor_api),
+    current_user: UserContext = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),
 ):
     """