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>

app/services/vendor_product_service.py

@@ -66,10 +66,7 @@ class VendorProductService:
         total = query.count()
 
         products = (
-            query.order_by(Product.updated_at.desc())
-            .offset(skip)
-            .limit(limit)
-            .all()
+            query.order_by(Product.updated_at.desc()).offset(skip).limit(limit).all()
         )
 
         result = []
@@ -138,8 +135,7 @@ class VendorProductService:
             .all()
         )
         return [
-            {"id": v.id, "name": v.name, "vendor_code": v.vendor_code}
-            for v in vendors
+            {"id": v.id, "name": v.name, "vendor_code": v.vendor_code} for v in vendors
         ]
 
     def get_product_detail(self, db: Session, product_id: int) -> dict:
@@ -212,8 +208,12 @@ class VendorProductService:
             "marketplace_translations": mp_translations,
             "vendor_translations": vendor_translations,
             # Timestamps
-            "created_at": product.created_at.isoformat() if product.created_at else None,
-            "updated_at": product.updated_at.isoformat() if product.updated_at else None,
+            "created_at": product.created_at.isoformat()
+            if product.created_at
+            else None,
+            "updated_at": product.updated_at.isoformat()
+            if product.updated_at
+            else None,
         }
 
     def remove_product(self, db: Session, product_id: int) -> dict:
@@ -257,8 +257,12 @@ class VendorProductService:
             "image_url": product.effective_primary_image_url,
             "source_marketplace": mp.marketplace if mp else None,
             "source_vendor": mp.vendor_name if mp else None,
-            "created_at": product.created_at.isoformat() if product.created_at else None,
-            "updated_at": product.updated_at.isoformat() if product.updated_at else None,
+            "created_at": product.created_at.isoformat()
+            if product.created_at
+            else None,
+            "updated_at": product.updated_at.isoformat()
+            if product.updated_at
+            else None,
         }