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>

app/api/main.py

@@ -5,13 +5,12 @@ API router configuration for multi-tenant ecommerce platform.
 This module provides:
 - API version 1 route aggregation
 - Route organization by user type (admin, vendor, storefront)
-- Proper route prefixing and tagging
+- Auto-discovery of module routes
 """
 
 from fastapi import APIRouter
 
-from app.api.v1 import admin, platform, storefront, vendor
-from app.api.v1.shared import language, webhooks
+from app.api.v1 import admin, public, storefront, vendor, webhooks
 
 api_router = APIRouter()
 
@@ -38,16 +37,17 @@ api_router.include_router(vendor.router, prefix="/v1/vendor", tags=["vendor"])
 api_router.include_router(storefront.router, prefix="/v1/storefront", tags=["storefront"])
 
 # ============================================================================
-# PLATFORM ROUTES (Public marketing and signup)
-# Prefix: /api/v1/platform
+# PUBLIC ROUTES (Unauthenticated endpoints)
+# Prefix: /api/v1/public
+# Includes: /signup, /pricing, /letzshop-vendors, /language
 # ============================================================================
 
-api_router.include_router(platform.router, prefix="/v1/platform", tags=["platform"])
+api_router.include_router(public.router, prefix="/v1/public", tags=["public"])
 
 # ============================================================================
-# SHARED ROUTES (Cross-context utilities)
-# Prefix: /api/v1
+# WEBHOOK ROUTES (External service callbacks via auto-discovery)
+# Prefix: /api/v1/webhooks
+# Includes: /stripe
 # ============================================================================
 
-api_router.include_router(language.router, prefix="/v1", tags=["language"])
-api_router.include_router(webhooks.router, prefix="/v1", tags=["webhooks"])
+api_router.include_router(webhooks.router, prefix="/v1/webhooks", tags=["webhooks"])