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/database/test_inventory.py

@@ -1,5 +1,6 @@
 # tests/unit/models/database/test_inventory.py
 """Unit tests for Inventory database model."""
+
 import pytest
 from sqlalchemy.exc import IntegrityError
 
@@ -56,7 +57,9 @@ class TestInventoryModel:
             db.add(inventory2)
             db.commit()
 
-    def test_inventory_same_product_different_location(self, db, test_vendor, test_product):
+    def test_inventory_same_product_different_location(
+        self, db, test_vendor, test_product
+    ):
         """Test same product can have inventory in different locations."""
         inventory1 = Inventory(
             product_id=test_product.id,