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/svelte.config.js

@@ -0,0 +1,5 @@
+import { vitePreprocess } from '@astrojs/svelte';
+
+export default {
+	preprocess: vitePreprocess(),
+}