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>

models/database/vendor.py

@@ -47,7 +47,9 @@ class Vendor(Base, TimestampMixin):
     subdomain = Column(
         String(100), unique=True, nullable=False, index=True
     )  # Unique, non-nullable subdomain column with indexing
-    name = Column(String, nullable=False)  # Non-nullable name column for the vendor (brand name)
+    name = Column(
+        String, nullable=False
+    )  # Non-nullable name column for the vendor (brand name)
     description = Column(Text)  # Optional text description column for the vendor
 
     # Letzshop URLs - multi-language support (brand-specific marketplace feeds)
@@ -287,13 +289,16 @@ class Vendor(Base, TimestampMixin):
         company = self.company
         return {
             "contact_email": self.effective_contact_email,
-            "contact_email_inherited": self.contact_email is None and company is not None,
+            "contact_email_inherited": self.contact_email is None
+            and company is not None,
             "contact_phone": self.effective_contact_phone,
-            "contact_phone_inherited": self.contact_phone is None and company is not None,
+            "contact_phone_inherited": self.contact_phone is None
+            and company is not None,
             "website": self.effective_website,
             "website_inherited": self.website is None and company is not None,
             "business_address": self.effective_business_address,
-            "business_address_inherited": self.business_address is None and company is not None,
+            "business_address_inherited": self.business_address is None
+            and company is not None,
             "tax_number": self.effective_tax_number,
             "tax_number_inherited": self.tax_number is None and company is not None,
         }