Fix admin interface issues and 404 errors

- Create adminEvents.js router to handle /api/admin/events endpoints
- Mount events router in admin.js to fix 404 errors
- Fix admin layout CSS - changed from static to flex layout
- Update AdminSidebar positioning from static to relative
- Add missing PUT endpoints for general and security settings
- Fix frontend environment variables in docker-compose.local.yml
- Add build args to Dockerfile.dev for environment variables
- Update CORS to accept requests from all dev servers
- Remove unused imports from SettingsPage

This fixes:
- Events page 404 error
- Admin layout misalignment (sidebar and content on different rows)
- Settings page not loading
- CORS issues between frontend and backend

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

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

docker-compose.local.yml

@@ -42,6 +42,10 @@ services:
     build:
       context: ./frontend
       dockerfile: Dockerfile.dev
+      args:
+        - VITE_API_URL=http://localhost:3001
+        - VITE_UMAMI_URL=
+        - VITE_UMAMI_WEBSITE_ID=
     ports:
       - "3005:80"
     environment:
@@ -65,6 +69,9 @@ services:
       - "3002:5173"
     environment:
       - NODE_ENV=development
+      - VITE_API_URL=http://localhost:3001
+      - VITE_UMAMI_URL=
+      - VITE_UMAMI_WEBSITE_ID=
     volumes:
       - ./frontend:/app
       - /app/node_modules