feat: modernize UI with Astro+Svelte and optimize Docker build

- Migrated frontend to Astro + Svelte 5 for cyberpunk aesthetic
- Switched to Bun for faster frontend builds
- Implemented multi-stage Docker build for smaller image size
- Refactored backend to serve static assets and proxy API requests
- Added recovery mode for manual file management

ui/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "ui",
+  "type": "module",
+  "version": "0.0.1",
+  "scripts": {
+    "dev": "astro dev",
+    "build": "astro build",
+    "preview": "astro preview",
+    "astro": "astro"
+  },
+  "dependencies": {
+    "@astrojs/svelte": "^7.2.5",
+    "@tailwindcss/vite": "^4.1.18",
+    "astro": "^5.17.1",
+    "svelte": "^5.49.2",
+    "tailwindcss": "^4.1.18",
+    "typescript": "^5.9.3"
+  }
+}