refactor: migrate vendor APIs to token-based context and consolidate architecture

## Vendor-in-Token Architecture (Complete Migration)
- Migrate all vendor API endpoints from require_vendor_context() to token_vendor_id
- Update permission dependencies to extract vendor from JWT token
- Add vendor exceptions: VendorAccessDeniedException, VendorOwnerOnlyException,
  InsufficientVendorPermissionsException
- Shop endpoints retain require_vendor_context() for URL-based detection
- Add AUTH-004 architecture rule enforcing vendor context patterns
- Fix marketplace router missing /marketplace prefix

## Exception Pattern Fixes (API-003/API-004)
- Services raise domain exceptions, endpoints let them bubble up
- Add code_quality and content_page exception modules
- Move business logic from endpoints to services (admin, auth, content_page)
- Fix exception handling in admin, shop, and vendor endpoints

## Tailwind CSS Consolidation
- Consolidate CSS to per-area files (admin, vendor, shop, platform)
- Remove shared/cdn-fallback.html and shared/css/tailwind.min.css
- Update all templates to use area-specific Tailwind output files
- Remove Node.js config (package.json, postcss.config.js, tailwind.config.js)

## Documentation & Cleanup
- Update vendor-in-token-architecture.md with completed migration status
- Update architecture-rules.md with new rules
- Move migration docs to docs/development/migration/
- Remove duplicate/obsolete documentation files
- Merge pytest.ini settings into pyproject.toml

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docs/frontend/admin/page-templates.md

@@ -1585,7 +1585,7 @@ async applyFilters() {
 // marketplace.js
 return {
     ...data(),
-    currentPage: 'marketplace',  // Highlights "Marketplace Import" in sidebar
+    currentPage: 'marketplace',  // Highlights "Marketplace" in sidebar
     // ...
 };
 
@@ -1597,6 +1597,28 @@ return {
 };
 ```
 
+### Collapsible Sections
+
+Sidebar sections are collapsible with state persisted to localStorage:
+
+```javascript
+// Section keys used in openSections state
+{
+    platformAdmin: true,   // Platform Administration (default open)
+    contentMgmt: false,    // Content Management
+    devTools: false,       // Developer Tools
+    monitoring: false      // Platform Monitoring
+}
+
+// Toggle a section
+toggleSection('devTools');
+
+// Check if section is open
+if (openSections.devTools) { ... }
+```
+
+See [Sidebar Navigation](../shared/sidebar.md) for full documentation.
+
 ---
 
 ## 🎨 UI Patterns