fix: correct tojson|safe usage in templates and update validator

- Remove |safe from |tojson in HTML attributes (x-data) - quotes must
  become " for browsers to parse correctly
- Update LANG-002 and LANG-003 architecture rules to document correct
  |tojson usage patterns:
  - HTML attributes: |tojson (no |safe)
  - Script blocks: |tojson|safe
- Fix validator to warn when |tojson|safe is used in x-data (breaks
  HTML attribute parsing)
- Improve code quality across services, APIs, and tests

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

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

tests/integration/workflows/test_integration.py

@@ -7,6 +7,7 @@ Tests complete workflows using actual API endpoints:
 - Admin product listing workflow
 - Marketplace import workflow
 """
+
 import uuid
 
 import pytest
@@ -49,7 +50,9 @@ class TestIntegrationFlows:
         vendors = response.json()
         assert any(v["vendor_code"] == vendor["vendor_code"] for v in vendors)
 
-    def test_admin_product_listing_workflow(self, client, admin_headers, test_marketplace_product):
+    def test_admin_product_listing_workflow(
+        self, client, admin_headers, test_marketplace_product
+    ):
         """Test admin product listing and search workflow"""
         # 1. List all products
         response = client.get("/api/v1/admin/products", headers=admin_headers)