feat: Enhance ticketing system with categories, templates, SLA tracking, and fix frontend integration

- Add ticket categories (billing, technical, feature_request, etc.) with type-specific options
- Add TicketTemplate and CannedResponse models for quick ticket creation
- Implement SLA tracking with due_at and first_response_at fields
- Add is_platform_admin and is_customer helper functions to fix permission checks
- Register models in Django admin with filters and fieldsets
- Enhance signals with error handling for WebSocket notifications
- Fix frontend API URLs for templates and canned responses
- Update PlatformSupport page to use real ticketing API
- Add comprehensive i18n translations for all ticket fields

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/package.json

@@ -4,6 +4,8 @@
   "version": "0.0.0",
   "type": "module",
   "dependencies": {
+    "@dnd-kit/core": "^6.3.1",
+    "@dnd-kit/utilities": "^3.2.2",
     "@stripe/connect-js": "^3.3.31",
     "@stripe/react-connect-js": "^3.3.31",
     "@tanstack/react-query": "^5.90.10",
@@ -15,6 +17,7 @@
     "lucide-react": "^0.554.0",
     "react": "^19.2.0",
     "react-dom": "^19.2.0",
+    "react-hot-toast": "^2.6.0",
     "react-i18next": "^16.3.5",
     "react-phone-number-input": "^3.4.14",
     "react-router-dom": "^7.9.6",