Build music-quiz installer and management site per spec

Implements the full spec described in README.md:

Management site (Node + TypeScript + Express + EJS):
- Public main page lists packs registered in manifest.json.
- /op login (account.json, internal-only), /op/dashboard manages packs
  with horizontal-scroll cards, add/select-and-delete flow, and the
  /op/dashboard/:packName editor (Mojang release dropdown, dynamic
  mods/resourcepacks lists, platform/RAM fields, file rename).
- Routes for /manifest.json (public) and /file/* (server pack files).
- Middleware blocks /account.json and /manifest/* directory access.

Installer (Electron):
- Five page renderer driven by IPC (preload contextBridge API):
  pack pick → single/multi → server install (path no-Korean check, JDK
  detect, file download, EULA, RAM gating, local web config editor,
  UPnP/port-forward check) → client install (.mc_custom mods +
  resourcepacks + launcher_profiles.json gameDir/javaArgs) → finish
  toggles (server folder, shortcut, server start, launcher start).

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

manifest/music-quiz.json

@@ -0,0 +1,25 @@
+{
+  "name": "음악퀴즈 v1",
+  "mcVersion": "1.20.1",
+  "platform": {
+    "type": "forge",
+    "downloadUrl": "https://example.com/forge-installer.jar"
+  },
+  "mods": [
+    {
+      "name": "ExampleMod",
+      "downloadUrl": "https://example.com/examplemod.jar"
+    }
+  ],
+  "resourcepacks": [
+    {
+      "name": "ExampleResourcePack",
+      "downloadUrl": "https://example.com/resourcepack.zip"
+    }
+  ],
+  "serverMinRam": 2048,
+  "serverMaxRam": 8192,
+  "clientMinRam": 4096,
+  "clientRecommendedRam": 8192,
+  "packPath": "music-quiz/files"
+}