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>

docs/implementation/platform-marketing-homepage.md

@@ -53,7 +53,7 @@ Based on `docs/marketing/pricing.md`:
 
 ### 1. Marketing Homepage (`/`)
 
-**Template:** `app/templates/platform/homepage-wizamart.html`
+**Template:** `app/templates/public/homepage-wizamart.html`
 
 **Sections:**
 
@@ -84,7 +84,7 @@ Based on `docs/marketing/pricing.md`:
 
 ### 2. Pricing Page (`/pricing`)
 
-**Template:** `app/templates/platform/pricing.html`
+**Template:** `app/templates/public/pricing.html`
 
 Standalone page with:
 - Large tier cards
@@ -94,7 +94,7 @@ Standalone page with:
 
 ### 3. Find Your Shop (`/find-shop`)
 
-**Template:** `app/templates/platform/find-shop.html`
+**Template:** `app/templates/public/find-shop.html`
 
 - URL input with examples
 - Real-time Letzshop vendor lookup
@@ -103,7 +103,7 @@ Standalone page with:
 
 ### 4. Signup Wizard (`/signup`)
 
-**Template:** `app/templates/platform/signup.html`
+**Template:** `app/templates/public/signup.html`
 
 **4-Step Flow:**
 
@@ -121,7 +121,7 @@ Standalone page with:
 
 ### 5. Signup Success (`/signup/success`)
 
-**Template:** `app/templates/platform/signup-success.html`
+**Template:** `app/templates/public/signup-success.html`
 
 - Success confirmation
 - Next steps checklist
@@ -132,24 +132,24 @@ Standalone page with:
 
 ## API Endpoints
 
-All endpoints under `/api/v1/platform/`:
+All endpoints under `/api/v1/public/`:
 
 ### Pricing Endpoints
 
 ```
-GET /api/v1/platform/tiers
+GET /api/v1/public/tiers
     Returns all public subscription tiers
     Response: TierResponse[]
 
-GET /api/v1/platform/tiers/{tier_code}
+GET /api/v1/public/tiers/{tier_code}
     Returns specific tier by code
     Response: TierResponse
 
-GET /api/v1/platform/addons
+GET /api/v1/public/addons
     Returns all active add-on products
     Response: AddOnResponse[]
 
-GET /api/v1/platform/pricing
+GET /api/v1/public/pricing
     Returns complete pricing info (tiers + addons + trial_days)
     Response: PricingResponse
 ```
@@ -157,17 +157,17 @@ GET /api/v1/platform/pricing
 ### Letzshop Vendor Endpoints
 
 ```
-GET /api/v1/platform/letzshop-vendors
+GET /api/v1/public/letzshop-vendors
     Query params: ?search=&category=&city=&page=1&limit=20
     Returns paginated vendor list (placeholder for future)
     Response: LetzshopVendorListResponse
 
-POST /api/v1/platform/letzshop-vendors/lookup
+POST /api/v1/public/letzshop-vendors/lookup
     Body: { "url": "letzshop.lu/vendors/my-shop" }
     Returns vendor info from URL lookup
     Response: LetzshopLookupResponse
 
-GET /api/v1/platform/letzshop-vendors/{slug}
+GET /api/v1/public/letzshop-vendors/{slug}
     Returns vendor info by slug
     Response: LetzshopVendorInfo
 ```
@@ -175,17 +175,17 @@ GET /api/v1/platform/letzshop-vendors/{slug}
 ### Signup Endpoints
 
 ```
-POST /api/v1/platform/signup/start
+POST /api/v1/public/signup/start
     Body: { "tier_code": "professional", "is_annual": false }
     Creates signup session
     Response: { "session_id": "...", "tier_code": "...", "is_annual": false }
 
-POST /api/v1/platform/signup/claim-vendor
+POST /api/v1/public/signup/claim-vendor
     Body: { "session_id": "...", "letzshop_slug": "my-shop" }
     Claims Letzshop vendor for session
     Response: { "session_id": "...", "letzshop_slug": "...", "vendor_name": "..." }
 
-POST /api/v1/platform/signup/create-account
+POST /api/v1/public/signup/create-account
     Body: {
         "session_id": "...",
         "email": "user@example.com",
@@ -197,17 +197,17 @@ POST /api/v1/platform/signup/create-account
     Creates User, Company, Vendor, Stripe Customer
     Response: { "session_id": "...", "user_id": 1, "vendor_id": 1, "stripe_customer_id": "cus_..." }
 
-POST /api/v1/platform/signup/setup-payment
+POST /api/v1/public/signup/setup-payment
     Body: { "session_id": "..." }
     Creates Stripe SetupIntent
     Response: { "session_id": "...", "client_secret": "seti_...", "stripe_customer_id": "cus_..." }
 
-POST /api/v1/platform/signup/complete
+POST /api/v1/public/signup/complete
     Body: { "session_id": "...", "setup_intent_id": "seti_..." }
     Completes signup, attaches payment method
     Response: { "success": true, "vendor_code": "...", "vendor_id": 1, "redirect_url": "...", "trial_ends_at": "..." }
 
-GET /api/v1/platform/signup/session/{session_id}
+GET /api/v1/public/signup/session/{session_id}
     Returns session status for resuming signup
     Response: { "session_id": "...", "step": "...", ... }
 ```
@@ -430,7 +430,7 @@ STRIPE_TRIAL_DAYS=30
 
 ### Automated Tests
 
-Test files located in `tests/integration/api/v1/platform/`:
+Test files located in `tests/integration/api/v1/public/`:
 
 | File | Tests | Description |
 |------|-------|-------------|
@@ -440,7 +440,7 @@ Test files located in `tests/integration/api/v1/platform/`:
 
 **Run tests:**
 ```bash
-pytest tests/integration/api/v1/platform/ -v
+pytest tests/integration/api/v1/public/ -v
 ```
 
 **Test categories:**
@@ -479,15 +479,15 @@ pytest tests/integration/api/v1/platform/ -v
 
 ```bash
 # Get pricing
-curl http://localhost:8000/api/v1/platform/pricing
+curl http://localhost:8000/api/v1/public/pricing
 
 # Lookup vendor
-curl -X POST http://localhost:8000/api/v1/platform/letzshop-vendors/lookup \
+curl -X POST http://localhost:8000/api/v1/public/letzshop-vendors/lookup \
   -H "Content-Type: application/json" \
   -d '{"url": "letzshop.lu/vendors/test-shop"}'
 
 # Start signup
-curl -X POST http://localhost:8000/api/v1/platform/signup/start \
+curl -X POST http://localhost:8000/api/v1/public/signup/start \
   -H "Content-Type: application/json" \
   -d '{"tier_code": "professional", "is_annual": false}'
 ```