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/dashboard.py

@@ -1,6 +1,9 @@
 # app/api/v1/vendor/dashboard.py
 """
 Vendor dashboard and statistics endpoints.
+
+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
@@ -10,7 +13,7 @@ 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, VendorNotActiveException
+from app.exceptions import VendorNotActiveException
 from app.services.stats_service import stats_service
 from app.services.vendor_service import vendor_service
 from models.database.user import User
@@ -37,10 +40,6 @@ def get_vendor_dashboard_stats(
     Vendor is determined from the JWT token (vendor_id claim).
     Requires Authorization header (API endpoint).
     """
-    # Get vendor ID from token (set by get_current_vendor_api)
-    if not hasattr(current_user, "token_vendor_id"):
-        raise InvalidTokenException("Token missing vendor information. Please login again.")
-
     vendor_id = current_user.token_vendor_id
 
     # Get vendor object (raises VendorNotFoundException if not found)