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>

src/types/index.ts

@@ -8,13 +8,23 @@ export interface Library {
   coverExt: string | null
 }
 
+export type GamePlatform = 'windows' | 'linux' | 'macos'
+
+export interface GameFile {
+  path: string
+  platform: GamePlatform
+  filename: string
+  isAppBundle?: boolean
+}
+
 export interface Game {
   id: string
   item_key?: string
   title: string
   coverUrl: string | null
   wideCoverUrl: string | null
-  zipFiles: string[]
+  gameFiles: GameFile[]
+  platforms: GamePlatform[]
 }
 
 export interface GameSeries {