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/development/naming-conventions.md

@@ -53,7 +53,7 @@ app/api/v1/vendor/
 ├── inventory.py    # Handles inventory items
 └── settings.py     # Exception: not a resource collection
 
-app/api/v1/public/vendors/
+app/api/v1/platform/vendors/
 ├── products.py     # Public product catalog
 ├── orders.py       # Order placement
 └── auth.py         # Exception: authentication service