feat: add playability calculation API

- Auto-calculate playability from benchmark data (FPS, anti-cheat, upscaler dependency)
- Manual override by admins/contributors
- Clear override to revert to auto-calculated
- Three endpoints: /calculate/:gameId, /override/:gameId, /clear-override/:gameId
- Calculation logic: great (≥55 FPS, no upscaler), playable (≥30 FPS), needs_tweaks (≥20 FPS), unplayable (<20 FPS or anti-cheat unsupported)

lib/api/index.ts

@@ -17,3 +17,4 @@ export { adminCommentRoutes } from "./admin-comments"
 export { steamgridProxyRoutes } from "./steamgrid-proxy"
 export { gamesManualRoutes } from "./games-manual"
 export { compareRoutes } from "./compare"
+export { playabilityRoutes } from "./playability"