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>

public/manifest.webmanifest

@@ -5,7 +5,8 @@
   "lang": "fa",
   "dir": "rtl",
   "start_url": "/",
-  "display": "standalone",
+  "display": "fullscreen",
+  "display_override": ["fullscreen", "standalone", "minimal-ui"],
   "orientation": "any",
   "background_color": "#060c1f",
   "theme_color": "#060c1f",