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/unit/models/schema/test_product.py

@@ -1,14 +1,14 @@
 # tests/unit/models/schema/test_product.py
 """Unit tests for product Pydantic schemas."""
+
 import pytest
 from pydantic import ValidationError
 
 from models.schema.product import (
     ProductCreate,
-    ProductUpdate,
-    ProductResponse,
-    ProductDetailResponse,
     ProductListResponse,
+    ProductResponse,
+    ProductUpdate,
 )