feat: migrate from Next.js to pure Bun relay proxy

- Replace Next.js app router with standalone Bun.serve() entry point
- Add middleware stack: rate limiter, body limiter, structured logger, SSRF protection
- Add WebSocket bidirectional relay via x-relay-target header
- Implement error classification (DNS→502, timeouts→504, SSRF→403, rate→429)
- Remove all Next.js dependencies and config files
- Update deploy workflow, tsconfig, wrangler config for Bun deployment

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/deploy.yml

@@ -1,32 +1,15 @@
-name: Deploy to Cloudflare Workers
-
+name: Deploy
 on:
   push:
-    branches: [main, master]
-  workflow_dispatch:
-
+    branches: [master]
 jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-
-      - uses: actions/setup-node@v4
-        with:
-          node-version: '22'
-
       - uses: oven-sh/setup-bun@v2
         with:
           bun-version: latest
-
-      - name: Install dependencies
-        run: bun install
-
-      - name: Build worker
-        run: bun run build:worker
-
-      - name: Deploy to Cloudflare
-        run: bunx wrangler deploy
-        env:
-          CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
-          CLOUDFLARE_ACCOUNT_ID: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+      - run: bun install
+      - run: bun run build
+      - run: bun test