Add multi-platform game support with per-OS download detection

- Detect Windows (.zip), Linux (.tar.gz), and macOS (.dmg / .app bundle) game archives during scan
- Store GameFile[] with platform metadata in DB instead of plain zipFiles[]
- Stream .app bundles as on-the-fly zip archives via archiver
- Show WIN/LIN/MAC platform badge pills on GameCard and SeriesCard
- Auto-select the download matching the user's OS in GameDetailModal
- Persist cover URL to DB immediately on upload (no re-scan needed)
- Backward-compatible: legacy zipFiles entries map to platform 'windows'

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -12,6 +12,7 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
+    "archiver": "^7.0.1",
     "better-sqlite3": "^12.8.0",
     "fast-xml-parser": "^5.5.10",
     "iron-session": "^8.0.4",
@@ -23,6 +24,7 @@
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4.2.2",
+    "@types/archiver": "^7.0.0",
     "@types/better-sqlite3": "^7.6.13",
     "@types/node": "^25.5.0",
     "@types/node-cron": "^3.0.11",