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/.vscode/extensions.json

@@ -0,0 +1,4 @@
+{
+  "recommendations": ["astro-build.astro-vscode"],
+  "unwantedRecommendations": []
+}

ui/.vscode/launch.json

@@ -0,0 +1,11 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "command": "./node_modules/.bin/astro dev",
+      "name": "Development server",
+      "request": "launch",
+      "type": "node-terminal"
+    }
+  ]
+}