feat: sitemap remediation, PWA activation, search refinements, Steam Deck UX

Sitemap:
- Switch from ISR (revalidate=3600) to force-dynamic for per-request generation
- Flatten into single app/sitemap.ts with inlined static entries and DB queries
- NULL-safe syncStatus filter: ne(games.syncStatus, 'failed') OR isNull(games.syncStatus)
- Structured JSON logging for generated URLs and DB errors
- Delete lib/sitemap/* helpers and app/api/revalidate-sitemap route
- Add basic vitest coverage for sitemap exports

PWA & Offline:
- Add @serwist/next service worker (webpack build) with runtime caching
- Cache strategies: stale-while-revalidate for game pages, network-first for listings/API,
  cache-first for Steam CDN images
- Offline fallback page (public/offline.html)
- Manifest icons: 192px maskable + 512px any
- Viewport meta with viewport-fit=cover, user-scalable=no
- Apple mobile web app meta tags

Search / Filter Refinements:
- Multi-genre OR support in listing API (comma-separated genres)
- Device-scoped FPS filter (min/max FPS constrained to selected device)
- Client-side URL state sync via router.replace for shareable filtered views
- Initialize filter state from URL params on mount
- Auto-collapse filter panel on saved-filter load
- Fix multi-genre saved filter parsing (comma-separated)

Steam Deck / Touch / Gamepad UX:
- WCAG 2.1 AA touch targets (44x44px) on all filter controls
- .gamepad-focus CSS focus ring for controller navigation
- useGamepadNavigation hook: D-pad/left-stick roving tabindex, A/B/X/Y actions
- Integrate gamepad hook into games page (X=search, Y=toggle filters)

Chore:
- Bump version to 2026.0.97

next.config.ts

@@ -1,4 +1,5 @@
 import type { NextConfig } from "next";
+import withSerwist from "@serwist/next";
 import { version } from "./package.json";
 
 const nextConfig: NextConfig = {
@@ -43,4 +44,8 @@ const nextConfig: NextConfig = {
   },
 };
 
-export default nextConfig;
+export default withSerwist({
+  swSrc: "app/sw.ts",
+  swDest: "public/sw.js",
+  disable: process.env.NODE_ENV === "development",
+})(nextConfig);