refactor: enforce strict architecture rules and add Pydantic response models

- Update architecture rules to be stricter (API-003 now blocks ALL exception
  raising in endpoints, not just HTTPException)
- Update get_current_vendor_api dependency to guarantee token_vendor_id presence
- Remove redundant _get_vendor_from_token helpers from all vendor API files
- Move vendor access validation to service layer methods
- Add Pydantic response models for media, notification, and payment endpoints
- Add get_active_vendor_by_code service method for public vendor lookup
- Add get_import_job_for_vendor service method with vendor validation
- Update validation script to detect exception raising patterns in endpoints

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/api/v1/vendor/customers.py

@@ -1,9 +1,9 @@
-# Vendor customer management
 # app/api/v1/vendor/customers.py
 """
 Vendor customer management endpoints.
 
-Vendor Context: Uses token_vendor_id from JWT token (authenticated vendor API pattern)
+Vendor Context: Uses token_vendor_id from JWT token (authenticated vendor API pattern).
+The get_current_vendor_api dependency guarantees token_vendor_id is present.
 """
 
 import logging
@@ -13,7 +13,6 @@ from sqlalchemy.orm import Session
 
 from app.api.deps import get_current_vendor_api
 from app.core.database import get_db
-from app.exceptions import InvalidTokenException
 from app.services.vendor_service import vendor_service
 from models.database.user import User
 
@@ -21,13 +20,6 @@ router = APIRouter(prefix="/customers")
 logger = logging.getLogger(__name__)
 
 
-def _get_vendor_from_token(current_user: User, db: Session):
-    """Helper to get vendor from JWT token."""
-    if not hasattr(current_user, "token_vendor_id"):
-        raise InvalidTokenException("Token missing vendor information. Please login again.")
-    return vendor_service.get_vendor_by_id(db, current_user.token_vendor_id)
-
-
 @router.get("")
 def get_vendor_customers(
     skip: int = Query(0, ge=0),
@@ -46,7 +38,7 @@ def get_vendor_customers(
     - Support filtering by active status
     - Return paginated results
     """
-    vendor = _get_vendor_from_token(current_user, db)  # noqa: F841 - vendor will be used when implemented
+    vendor = vendor_service.get_vendor_by_id(db, current_user.token_vendor_id)  # noqa: F841
     return {
         "customers": [],
         "total": 0,
@@ -71,7 +63,7 @@ def get_customer_details(
     - Include order history
     - Include total spent, etc.
     """
-    vendor = _get_vendor_from_token(current_user, db)  # noqa: F841 - vendor will be used when implemented
+    vendor = vendor_service.get_vendor_by_id(db, current_user.token_vendor_id)  # noqa: F841
     return {"message": "Customer details coming in Slice 4"}
 
 
@@ -89,7 +81,7 @@ def get_customer_orders(
     - Filter by vendor_id
     - Return order details
     """
-    vendor = _get_vendor_from_token(current_user, db)  # noqa: F841 - vendor will be used when implemented
+    vendor = vendor_service.get_vendor_by_id(db, current_user.token_vendor_id)  # noqa: F841
     return {"orders": [], "message": "Customer orders coming in Slice 5"}
 
 
@@ -108,7 +100,7 @@ def update_customer(
     - Verify customer belongs to vendor
     - Update customer preferences
     """
-    vendor = _get_vendor_from_token(current_user, db)  # noqa: F841 - vendor will be used when implemented
+    vendor = vendor_service.get_vendor_by_id(db, current_user.token_vendor_id)  # noqa: F841
     return {"message": "Customer update coming in Slice 4"}
 
 
@@ -126,7 +118,7 @@ def toggle_customer_status(
     - Verify customer belongs to vendor
     - Log the change
     """
-    vendor = _get_vendor_from_token(current_user, db)  # noqa: F841 - vendor will be used when implemented
+    vendor = vendor_service.get_vendor_by_id(db, current_user.token_vendor_id)  # noqa: F841
     return {"message": "Customer status toggle coming in Slice 4"}
 
 
@@ -145,7 +137,7 @@ def get_customer_statistics(
     - Average order value
     - Last order date
     """
-    vendor = _get_vendor_from_token(current_user, db)  # noqa: F841 - vendor will be used when implemented
+    vendor = vendor_service.get_vendor_by_id(db, current_user.token_vendor_id)  # noqa: F841
     return {
         "total_orders": 0,
         "total_spent": 0.0,