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>

tests/unit/services/test_vendor_service.py

@@ -5,16 +5,16 @@ import uuid
 
 import pytest
 
-from app.exceptions import (
+from app.exceptions import ValidationException
+from app.modules.tenancy.exceptions import (
     InvalidVendorDataException,
-    MarketplaceProductNotFoundException,
-    ProductAlreadyExistsException,
     UnauthorizedVendorAccessException,
-    ValidationException,
     VendorAlreadyExistsException,
     VendorNotFoundException,
 )
-from app.services.vendor_service import VendorService
+from app.modules.marketplace.exceptions import MarketplaceProductNotFoundException
+from app.modules.catalog.exceptions import ProductAlreadyExistsException
+from app.modules.tenancy.services.vendor_service import VendorService
 from models.database.company import Company
 from models.database.vendor import Vendor
 from app.modules.catalog.schemas import ProductCreate
@@ -642,7 +642,7 @@ class TestVendorServiceUpdate:
         """Test update fails for unauthorized user."""
         from pydantic import BaseModel
 
-        from app.exceptions import InsufficientPermissionsException
+        from app.modules.tenancy.exceptions import InsufficientPermissionsException
         from models.database.user import User
 
         class VendorUpdate(BaseModel):
@@ -694,7 +694,7 @@ class TestVendorServiceUpdate:
         self, db, other_company, test_vendor
     ):
         """Test marketplace settings update fails for unauthorized user."""
-        from app.exceptions import InsufficientPermissionsException
+        from app.modules.tenancy.exceptions import InsufficientPermissionsException
         from models.database.user import User
 
         other_user = db.query(User).filter(User.id == other_company.owner_user_id).first()
@@ -722,7 +722,7 @@ class TestVendorServiceSingleton:
 
     def test_singleton_exists(self):
         """Test vendor_service singleton exists."""
-        from app.services.vendor_service import vendor_service
+        from app.modules.tenancy.services.vendor_service import vendor_service
 
         assert vendor_service is not None
         assert isinstance(vendor_service, VendorService)