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>

app/api/main.py

@@ -10,7 +10,7 @@ This module provides:
 
 from fastapi import APIRouter
 
-from app.api.v1 import admin, public, storefront, vendor, webhooks
+from app.api.v1 import admin, platform, storefront, vendor, webhooks
 
 api_router = APIRouter()
 
@@ -37,12 +37,12 @@ api_router.include_router(vendor.router, prefix="/v1/vendor", tags=["vendor"])
 api_router.include_router(storefront.router, prefix="/v1/storefront", tags=["storefront"])
 
 # ============================================================================
-# PUBLIC ROUTES (Unauthenticated endpoints)
-# Prefix: /api/v1/public
+# PLATFORM ROUTES (Unauthenticated endpoints)
+# Prefix: /api/v1/platform
 # Includes: /signup, /pricing, /letzshop-vendors, /language
 # ============================================================================
 
-api_router.include_router(public.router, prefix="/v1/public", tags=["public"])
+api_router.include_router(platform.router, prefix="/v1/platform", tags=["platform"])
 
 # ============================================================================
 # WEBHOOK ROUTES (External service callbacks via auto-discovery)