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/services/test_product_service.py

@@ -108,8 +108,7 @@ class TestProductService:
         assert existing_product_id in str(exc_info.value)
         assert exc_info.value.status_code == 409
         assert (
-            exc_info.value.details.get("marketplace_product_id")
-            == existing_product_id
+            exc_info.value.details.get("marketplace_product_id") == existing_product_id
         )
 
     def test_create_product_invalid_price(self, db):
@@ -224,7 +223,9 @@ class TestProductService:
         assert "Invalid GTIN format" in str(exc_info.value)
         assert exc_info.value.details.get("field") == "gtin"
 
-    def test_update_product_empty_title_preserves_existing(self, db, test_marketplace_product):
+    def test_update_product_empty_title_preserves_existing(
+        self, db, test_marketplace_product
+    ):
         """Test updating product with empty title preserves existing title in translation"""
         original_title = test_marketplace_product.get_title()
         update_data = MarketplaceProductUpdate(title="")
@@ -275,7 +276,9 @@ class TestProductService:
         self, db, test_marketplace_product_with_inventory
     ):
         """Test getting inventory info for product with inventory."""
-        marketplace_product = test_marketplace_product_with_inventory["marketplace_product"]
+        marketplace_product = test_marketplace_product_with_inventory[
+            "marketplace_product"
+        ]
         inventory = test_marketplace_product_with_inventory["inventory"]
 
         inventory_info = self.service.get_inventory_info(db, marketplace_product.gtin)
@@ -352,7 +355,10 @@ class TestMarketplaceProductServiceAdmin:
         # Find our test product in results
         found = False
         for p in products:
-            if p["marketplace_product_id"] == test_marketplace_product.marketplace_product_id:
+            if (
+                p["marketplace_product_id"]
+                == test_marketplace_product.marketplace_product_id
+            ):
                 found = True
                 assert p["id"] == test_marketplace_product.id
                 assert p["marketplace"] == test_marketplace_product.marketplace
@@ -429,9 +435,7 @@ class TestMarketplaceProductServiceAdmin:
 
     def test_get_admin_product_detail(self, db, test_marketplace_product):
         """Test getting admin product detail by ID."""
-        product = self.service.get_admin_product_detail(
-            db, test_marketplace_product.id
-        )
+        product = self.service.get_admin_product_detail(db, test_marketplace_product.id)
 
         assert product["id"] == test_marketplace_product.id
         assert (