fix: resolve architecture validation errors and warnings

- Fix JS-008: Replace raw fetch() with apiClient in letzshop-vendor-directory.js
- Fix JS-005: Add init guard to letzshop-vendor-directory.js
- Fix JS-004: Increase search region in validator (800→2000 chars) to detect
  currentPage in files with setup code before return statement
- Fix JS-001: Use centralized logger in media-picker.js
- Fix API-002: Move database query from onboarding.py to order_service.py
- Fix FE-001: Add noqa comment to search.html (shop uses custom themed pagination)
- Add audit validator to validate_all.py script
- Update frontend.yaml with vendor exclusion pattern

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.architecture-rules/frontend.yaml

@@ -24,6 +24,7 @@ javascript_rules:
         - "console.log('✅"
       auto_exclude_files:
         - "init-*.js"
+        - "vendor/"
 
   - id: "JS-002"
     name: "Use lowercase apiClient for API calls"
@@ -67,6 +68,8 @@ javascript_rules:
       recommended_pattern: |
         if (window._pageInitialized) return;
         window._pageInitialized = true;
+      auto_exclude_files:
+        - "vendor/"
 
   - id: "JS-006"
     name: "All async operations must have try/catch with error logging"