refactor: migrate templates and static files to self-contained modules

Templates Migration:
- Migrate admin templates to modules (tenancy, billing, monitoring, marketplace, etc.)
- Migrate vendor templates to modules (tenancy, billing, orders, messaging, etc.)
- Migrate storefront templates to modules (catalog, customers, orders, cart, checkout, cms)
- Migrate public templates to modules (billing, marketplace, cms)
- Keep shared templates in app/templates/ (base.html, errors/, partials/, macros/)
- Migrate letzshop partials to marketplace module

Static Files Migration:
- Migrate admin JS to modules: tenancy (23 files), core (5 files), monitoring (1 file)
- Migrate vendor JS to modules: tenancy (4 files), core (2 files)
- Migrate shared JS: vendor-selector.js to core, media-picker.js to cms
- Migrate storefront JS: storefront-layout.js to core
- Keep framework JS in static/ (api-client, utils, money, icons, log-config, lib/)
- Update all template references to use module_static paths

Naming Consistency:
- Rename static/platform/ to static/public/
- Rename app/templates/platform/ to app/templates/public/
- Update all extends and static references

Documentation:
- Update module-system.md with shared templates documentation
- Update frontend-structure.md with new module JS organization

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

scripts/debug_historical_import.py

@@ -5,7 +5,7 @@ import sys
 sys.path.insert(0, ".")
 
 from app.core.database import SessionLocal
-from app.services.letzshop.credentials_service import LetzshopCredentialsService
+from app.modules.marketplace.services.letzshop.credentials_service import LetzshopCredentialsService
 from app.modules.marketplace.models import LetzshopHistoricalImportJob
 
 

scripts/test_historical_import.py

@@ -597,7 +597,7 @@ def main():
         print(f"  Page {page}: {total} shipments fetched so far")
 
     # Import here to avoid issues if just doing debug
-    from app.services.letzshop.client_service import LetzshopClient
+    from app.modules.marketplace.services.letzshop.client_service import LetzshopClient
 
     # Create client and fetch
     with LetzshopClient(api_key=args.api_key) as client:

scripts/test_logging_system.py

@@ -90,7 +90,7 @@ def test_logging_endpoints():
     print("\n[4] Testing log settings...")
     try:
         from app.core.database import SessionLocal
-        from app.services.admin_settings_service import admin_settings_service
+        from app.modules.core.services.admin_settings_service import admin_settings_service
 
         db = SessionLocal()
         try: