feat: implement video site per README spec

- Express + EJS + express-session stack (auth/navbar ported from minecraft_launcher)
- Public: main folder list, folder video grid, internal popup player (/player/:videoId)
- Admin (/op): login, folder CRUD with right-click context menu + add-folder modal
- Admin folder: video grid with right-click edit/rename/delete, "영상 추가" -> editor
- Video editor: drag-drop upload, file picker, YouTube URL probe (ETA + 5분 경고),
  background yt-dlp download with progress polling, navbar title edit, trim controls,
  save runs ffmpeg trim (original preserved)
- Filesystem storage under data/folders/<name>/<videoId>/{meta.json, original.<ext>, edited.<ext>}

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tsconfig.json

@@ -0,0 +1,15 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "outDir": "dist",
+    "rootDir": "src",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "resolveJsonModule": true,
+    "forceConsistentCasingInFileNames": true
+  },
+  "include": ["src/**/*.ts"]
+}