refactor(js): move media.js to CMS module

Media library management is part of content management (CMS).
This matches the Python pattern where:
- Core media service (upload, storage) stays in platform
- Media library UI (browsing, organizing) goes to CMS module
- Media picker component stays shared (used by products, CMS, etc.)

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

docs/architecture/frontend-structure.md

@@ -338,7 +338,7 @@ app.mount("/static/modules/orders", StaticFiles(directory="app/modules/orders/st
 | **marketplace** | marketplace*.js, letzshop*.js | letzshop.js, marketplace.js, onboarding.js | - |
 | **monitoring** | monitoring.js, background-tasks.js, imports.js, logs.js | - | - |
 | **dev_tools** | testing-*.js, code-quality-*.js, icons-page.js, components.js | - | - |
-| **cms** | content-pages.js, content-page-edit.js | content-pages.js, content-page-edit.js | - |
+| **cms** | content-pages.js, content-page-edit.js | content-pages.js, content-page-edit.js, media.js | - |
 | **analytics** | - | analytics.js | - |
 
 ### Platform Static Files (Not in Modules)
@@ -363,7 +363,6 @@ These files remain in `static/` because they're platform-level, not module-speci
 - `profile.js` - Vendor account settings
 - `settings.js` - Vendor configuration
 - `team.js` - Team member management
-- `media.js` - Media library (shared across products)
 
 **Shared Utilities (`static/shared/js/`):**
 - `api-client.js` - Core HTTP client with auth