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>

src/server/routes/index.ts

@@ -0,0 +1,23 @@
+import { Router } from 'express'
+import { listPackKeys, loadPackDefinition, readManifest } from '../../shared/store'
+
+export const indexRouter = Router()
+
+indexRouter.get('/', async (_req, res, next) => {
+  try {
+    const manifest = await readManifest()
+    const definitionMap = new Map<string, Awaited<ReturnType<typeof loadPackDefinition>>>()
+    const keys = await listPackKeys()
+    for (const key of keys) {
+      definitionMap.set(key, await loadPackDefinition(key))
+    }
+    const packs = manifest.packs.map((entry) => ({
+      name: entry.name,
+      file: entry.file,
+      definition: definitionMap.get(entry.file) ?? null
+    }))
+    res.render('index', { packs })
+  } catch (error) {
+    next(error)
+  }
+})