✨ feat: add Vercel deployment support and optimize build configuration

Configure project for Vercel deployment with comprehensive build optimization:

- Add Vercel deployment configuration (vercel.json)
  - Configure build commands and output directory
  - Set up Bilibili API proxy rewrites
  - Add security response headers (X-Content-Type-Options, X-Frame-Options, X-XSS-Protection)

- Integrate Tailwind CSS 4.x build system
  - Add PostCSS configuration with @tailwindcss/postcss plugin
  - Create Tailwind CSS configuration with content scanning paths
  - Set up index.css with Tailwind imports and custom styles
  - Add Tailwind CSS 4.x and dependencies to package.json

- Optimize HTML and entry files
  - Remove CDN-based Tailwind CSS in favor of local build
  - Add Google Fonts preconnect for better performance
  - Import CSS in index.tsx for proper bundling

- Update README with deployment instructions
  - Add one-click Vercel deployment button
  - Separate local development and deployment sections

Tech Stack Updates:
- Tailwind CSS 4.1.17 with new PostCSS architecture
- Autoprefixer 10.4.22 for CSS compatibility
- PostCSS 8.5.6 for CSS processing

Build Verification:
- Development server runs successfully on port 3000
- Production build completes in ~860ms
- Output: 13KB CSS (gzipped: 2.94KB), 260KB JS (gzipped: 80KB)

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

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

index.css

@@ -0,0 +1,29 @@
+@import "tailwindcss";
+
+@theme {
+  --font-family-sans: 'Inter', sans-serif;
+  --font-family-mono: 'JetBrains Mono', monospace;
+}
+
+body {
+  font-family: var(--font-family-sans);
+  margin: 0;
+  overflow: hidden;
+}
+
+.custom-scrollbar::-webkit-scrollbar {
+  width: 8px;
+}
+
+.custom-scrollbar::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+.custom-scrollbar::-webkit-scrollbar-thumb {
+  background-color: rgba(255, 255, 255, 0.15);
+  border-radius: 999px;
+}
+
+.custom-scrollbar::-webkit-scrollbar-thumb:hover {
+  background-color: rgba(255, 255, 255, 0.3);
+}