feat: add JSON editor for config

- Add a JSON editor using Monaco Editor to allow raw editing of the configuration.
- The editor is presented as a full-screen dialog that slides up from the bottom.
- Includes 'Save' and 'Save and Restart' functionality with internationalized labels and toast notifications for success/failure.

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

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

ui/package.json

@@ -10,6 +10,7 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "@monaco-editor/react": "^4.7.0",
     "@radix-ui/react-dialog": "^1.1.14",
     "@radix-ui/react-label": "^2.1.7",
     "@radix-ui/react-popover": "^1.1.14",