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/v1/webhooks/__init__.py

@@ -0,0 +1,29 @@
+# app/api/v1/webhooks/__init__.py
+"""
+Webhook API endpoints for external service callbacks.
+
+Auto-discovers and aggregates webhook routes from self-contained modules:
+- payments: /stripe (Stripe payment webhooks)
+
+Webhooks use signature verification for security, not user authentication.
+"""
+
+from fastapi import APIRouter
+
+from app.modules.routes import get_webhooks_api_routes
+
+router = APIRouter()
+
+# Auto-discover webhook routes from modules
+for route_info in get_webhooks_api_routes():
+    if route_info.custom_prefix:
+        router.include_router(
+            route_info.router,
+            prefix=route_info.custom_prefix,
+            tags=route_info.tags,
+        )
+    else:
+        router.include_router(
+            route_info.router,
+            tags=route_info.tags,
+        )