mobile: fullscreen (immersive Android + PWA) + auto-hide reported nudity avatars

Fullscreen on mobile:
- Android (Capacitor): MainActivity now runs edge-to-edge and hides the status +
  navigation bars (immersive, transient-on-swipe), re-asserted on focus.
- PWA: manifest display -> "fullscreen" with display_override fallback chain;
  viewport gains viewport-fit: cover for proper safe-area/edge-to-edge handling.

Moderation auto-hide:
- ProfileService.ReportUser now de-dupes nudity reports per reporter and, once
  NudityHideThreshold (3) distinct players flag a target's avatar as nudity,
  auto-removes their custom photo (reverts to default avatar). Counted from the
  ledger, so still no schema change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/layout.tsx

@@ -18,6 +18,7 @@ export const viewport: Viewport = {
   initialScale: 1,
   maximumScale: 1,
   userScalable: false,
+  viewportFit: "cover",
 };
 
 export default function RootLayout({