feat: comprehensive React SPA replacing Jinja2 UI

- New dark UI with 7 tabs: Rig, FX Chain, Models, IRs, Presets, Settings, Record
- All screens wired to live API endpoints
- Real-time state via WebSocket + polling fallback
- Models screen: list/load/unload/upload NAM files + Tone3000 search/install
- IRs screen: list/load/unload/upload IR files + Tone3000 search/install
- Presets screen: browse banks, activate, save, delete
- Settings screen: WiFi scan/connect/hotspot, Bluetooth/MIDI, 4CM routing
- Rig screen: live state, volume, bypass, tuner, signal chain
- FX Chain screen: block params, per-block bypass
- Serves at / instead of /ui
- Built with Vite, ~71KB gzipped

frontend-react/eslint.config.js

@@ -0,0 +1,21 @@
+import js from '@eslint/js'
+import globals from 'globals'
+import reactHooks from 'eslint-plugin-react-hooks'
+import reactRefresh from 'eslint-plugin-react-refresh'
+import { defineConfig, globalIgnores } from 'eslint/config'
+
+export default defineConfig([
+  globalIgnores(['dist']),
+  {
+    files: ['**/*.{js,jsx}'],
+    extends: [
+      js.configs.recommended,
+      reactHooks.configs.flat.recommended,
+      reactRefresh.configs.vite,
+    ],
+    languageOptions: {
+      globals: globals.browser,
+      parserOptions: { ecmaFeatures: { jsx: true } },
+    },
+  },
+])