chore(deps): update node engine requirement and clean server externals

Remove 'ffmpeg-static' from server external packages in Next.js config and
specify Node.js 22.x as required engine in package.json to align with
deployment environment.

next.config.ts

@@ -24,7 +24,6 @@ const computeLocal = computeMode === 'local';
 const isVercel = process.env.VERCEL === '1';
 const serverExternalPackages = [
   '@napi-rs/canvas',
-  'ffmpeg-static',
   'better-sqlite3',
   ...(computeLocal ? ['onnxruntime-node', '@huggingface/tokenizers'] : []),
 ];

package.json

@@ -2,6 +2,9 @@
   "name": "openreader",
   "version": "3.0.0",
   "private": true,
+  "engines": {
+    "node": "22.x"
+  },
   "packageManager": "pnpm@10.33.4",
   "scripts": {
     "dev": "node scripts/openreader-entrypoint.mjs -- pnpm dev:raw",