refactor: rename public routes and templates to platform

Complete the public -> platform naming migration across the codebase.
This aligns with the naming convention where "platform" refers to
the marketing/public-facing pages of the platform itself.

Changes:
- Update all imports from public to platform modules
- Update template references from public/ to platform/
- Update route registrations to use platform prefix
- Update documentation to reflect new naming
- Update test files for platform API endpoints

Files affected:
- app/api/main.py - router imports
- app/modules/*/routes/*/platform.py - route definitions
- app/modules/*/templates/*/platform/ - template files
- app/modules/routes.py - route discovery
- docs/* - documentation updates
- tests/integration/api/v1/platform/ - test files

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

docs/implementation/platform-marketing-homepage.md

@@ -132,24 +132,24 @@ Standalone page with:
 
 ## API Endpoints
 
-All endpoints under `/api/v1/public/`:
+All endpoints under `/api/v1/platform/`:
 
 ### Pricing Endpoints
 
 ```
-GET /api/v1/public/tiers
+GET /api/v1/platform/tiers
     Returns all public subscription tiers
     Response: TierResponse[]
 
-GET /api/v1/public/tiers/{tier_code}
+GET /api/v1/platform/tiers/{tier_code}
     Returns specific tier by code
     Response: TierResponse
 
-GET /api/v1/public/addons
+GET /api/v1/platform/addons
     Returns all active add-on products
     Response: AddOnResponse[]
 
-GET /api/v1/public/pricing
+GET /api/v1/platform/pricing
     Returns complete pricing info (tiers + addons + trial_days)
     Response: PricingResponse
 ```
@@ -157,17 +157,17 @@ GET /api/v1/public/pricing
 ### Letzshop Vendor Endpoints
 
 ```
-GET /api/v1/public/letzshop-vendors
+GET /api/v1/platform/letzshop-vendors
     Query params: ?search=&category=&city=&page=1&limit=20
     Returns paginated vendor list (placeholder for future)
     Response: LetzshopVendorListResponse
 
-POST /api/v1/public/letzshop-vendors/lookup
+POST /api/v1/platform/letzshop-vendors/lookup
     Body: { "url": "letzshop.lu/vendors/my-shop" }
     Returns vendor info from URL lookup
     Response: LetzshopLookupResponse
 
-GET /api/v1/public/letzshop-vendors/{slug}
+GET /api/v1/platform/letzshop-vendors/{slug}
     Returns vendor info by slug
     Response: LetzshopVendorInfo
 ```
@@ -175,17 +175,17 @@ GET /api/v1/public/letzshop-vendors/{slug}
 ### Signup Endpoints
 
 ```
-POST /api/v1/public/signup/start
+POST /api/v1/platform/signup/start
     Body: { "tier_code": "professional", "is_annual": false }
     Creates signup session
     Response: { "session_id": "...", "tier_code": "...", "is_annual": false }
 
-POST /api/v1/public/signup/claim-vendor
+POST /api/v1/platform/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/public/signup/create-account
+POST /api/v1/platform/signup/create-account
     Body: {
         "session_id": "...",
         "email": "user@example.com",
@@ -197,17 +197,17 @@ POST /api/v1/public/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/public/signup/setup-payment
+POST /api/v1/platform/signup/setup-payment
     Body: { "session_id": "..." }
     Creates Stripe SetupIntent
     Response: { "session_id": "...", "client_secret": "seti_...", "stripe_customer_id": "cus_..." }
 
-POST /api/v1/public/signup/complete
+POST /api/v1/platform/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/public/signup/session/{session_id}
+GET /api/v1/platform/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/public/`:
+Test files located in `tests/integration/api/v1/platform/`:
 
 | File | Tests | Description |
 |------|-------|-------------|
@@ -440,7 +440,7 @@ Test files located in `tests/integration/api/v1/public/`:
 
 **Run tests:**
 ```bash
-pytest tests/integration/api/v1/public/ -v
+pytest tests/integration/api/v1/platform/ -v
 ```
 
 **Test categories:**
@@ -479,15 +479,15 @@ pytest tests/integration/api/v1/public/ -v
 
 ```bash
 # Get pricing
-curl http://localhost:8000/api/v1/public/pricing
+curl http://localhost:8000/api/v1/platform/pricing
 
 # Lookup vendor
-curl -X POST http://localhost:8000/api/v1/public/letzshop-vendors/lookup \
+curl -X POST http://localhost:8000/api/v1/platform/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/public/signup/start \
+curl -X POST http://localhost:8000/api/v1/platform/signup/start \
   -H "Content-Type: application/json" \
   -d '{"tier_code": "professional", "is_annual": false}'
 ```