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>

android/app/src/main/java/com/bargevasat/app/MainActivity.java

@@ -1,5 +1,38 @@
 package com.bargevasat.app;
 
+import android.os.Bundle;
+import androidx.core.view.WindowCompat;
+import androidx.core.view.WindowInsetsCompat;
+import androidx.core.view.WindowInsetsControllerCompat;
 import com.getcapacitor.BridgeActivity;
 
-public class MainActivity extends BridgeActivity {}
+/**
+ * Runs the game edge-to-edge and hides the Android status + navigation bars for
+ * a fullscreen, console-like experience (they reappear transiently on a swipe).
+ */
+public class MainActivity extends BridgeActivity {
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        enableImmersive();
+    }
+
+    @Override
+    public void onWindowFocusChanged(boolean hasFocus) {
+        super.onWindowFocusChanged(hasFocus);
+        // Re-assert immersive mode whenever the window regains focus (e.g. after a
+        // system dialog, or the bars were swiped in).
+        if (hasFocus) enableImmersive();
+    }
+
+    private void enableImmersive() {
+        WindowCompat.setDecorFitsSystemWindows(getWindow(), false);
+        WindowInsetsControllerCompat controller =
+            WindowCompat.getInsetsController(getWindow(), getWindow().getDecorView());
+        if (controller != null) {
+            controller.hide(WindowInsetsCompat.Type.systemBars());
+            controller.setSystemBarsBehavior(
+                WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE);
+        }
+    }
+}