Add OOTT-branded native splash for Android and iOS

Replace the vanilla Flutter splash with the OOTT wordmark (Barlow
Condensed Bold) on the Gruvbox-dark background, matching the in-app
AppBar badge. Generated via flutter_native_splash, covering legacy
Android, the Android 12+ SplashScreen API, and iOS (light + dark).

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

frontend/ios/Runner/Assets.xcassets/LaunchImage.imageset/Contents.json

@@ -1,23 +1,56 @@
 {
   "images" : [
     {
-      "idiom" : "universal",
       "filename" : "LaunchImage.png",
+      "idiom" : "universal",
       "scale" : "1x"
     },
     {
+      "appearances" : [
+        {
+          "appearance" : "luminosity",
+          "value" : "dark"
+        }
+      ],
+      "filename" : "LaunchImageDark.png",
       "idiom" : "universal",
+      "scale" : "1x"
+    },
+    {
       "filename" : "LaunchImage@2x.png",
+      "idiom" : "universal",
       "scale" : "2x"
     },
     {
+      "appearances" : [
+        {
+          "appearance" : "luminosity",
+          "value" : "dark"
+        }
+      ],
+      "filename" : "LaunchImageDark@2x.png",
       "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
       "filename" : "LaunchImage@3x.png",
+      "idiom" : "universal",
+      "scale" : "3x"
+    },
+    {
+      "appearances" : [
+        {
+          "appearance" : "luminosity",
+          "value" : "dark"
+        }
+      ],
+      "filename" : "LaunchImageDark@3x.png",
+      "idiom" : "universal",
       "scale" : "3x"
     }
   ],
   "info" : {
-    "version" : 1,
-    "author" : "xcode"
+    "author" : "xcode",
+    "version" : 1
   }
 }