Use the OOTT brand icon as the app launcher icon on all platforms

The app shipped Flutter's default icon on every platform. Add
flutter_launcher_icons (mirroring the existing flutter_native_splash
setup) with an OOTT wordmark on the brand orange (#fe8019) and
regenerate the native icon sets for iOS, Android, macOS, Windows and
web.

Android uses an adaptive icon (orange background + inset transparent
foreground) so the mark survives any launcher mask; the square
full-bleed source is used elsewhere where the platform applies its own
corner mask. Source images live under assets/icon/.

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

frontend/web/manifest.json

@@ -3,19 +3,19 @@
     "short_name": "frontend",
     "start_url": ".",
     "display": "standalone",
-    "background_color": "#0175C2",
-    "theme_color": "#0175C2",
+    "background_color": "#fe8019",
+    "theme_color": "#fe8019",
     "description": "A new Flutter project.",
     "orientation": "portrait-primary",
     "prefer_related_applications": false,
     "icons": [
         {
-            "src": "icons/android-chrome-192x192.png",
+            "src": "icons/Icon-192.png",
             "sizes": "192x192",
             "type": "image/png"
         },
         {
-            "src": "icons/android-chrome-512x512.png",
+            "src": "icons/Icon-512.png",
             "sizes": "512x512",
             "type": "image/png"
         },
@@ -32,4 +32,4 @@
             "purpose": "maskable"
         }
     ]
-}
+}