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

lib/sitemap/__tests__/sitemap.test.ts

@@ -0,0 +1,34 @@
+import { describe, it, expect, vi } from "vitest"
+
+vi.mock("@/lib/db/index", () => ({
+  db: {
+    select: vi.fn().mockReturnValue({
+      from: vi.fn().mockReturnValue({
+        where: vi.fn().mockResolvedValue([]),
+      }),
+    }),
+  },
+}))
+
+vi.mock("@/lib/db/schema", () => ({
+  games: { id: "id", updatedAt: "updatedAt", capsuleImage: "capsuleImage", syncStatus: "syncStatus" },
+  hardware: { slug: "slug", createdAt: "createdAt" },
+}))
+
+vi.mock("drizzle-orm", () => ({
+  or: vi.fn((...args) => args[0]),
+  ne: vi.fn((col) => col),
+  isNull: vi.fn((col) => col),
+}))
+
+describe("Sitemap Generator", () => {
+  it("exports dynamic = force-dynamic", async () => {
+    const mod = await import("@/app/sitemap")
+    expect(mod.dynamic).toBe("force-dynamic")
+  })
+
+  it("default export is a function", async () => {
+    const mod = await import("@/app/sitemap")
+    expect(typeof mod.default).toBe("function")
+  })
+})