Add UILaunchScreen — fixes screen letterboxing

Without UILaunchScreen (or UILaunchStoryboardName) in Info.plist, iOS runs
the app in legacy device-scaling mode and letterboxes it inside a smaller
iPhone-sized window. That's where the unexplained black bars at the top and
bottom of every screenshot came from — the SwiftUI layout was correct all
along, but iOS was rendering the entire app inside a ~75% viewport.

Adding an empty UILaunchScreen dict opts into modern full-screen rendering.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Screens/Resources/Info.plist

@@ -38,6 +38,11 @@
         <key>UIApplicationSupportsMultipleScenes</key>
         <true/>
     </dict>
+    <key>UILaunchScreen</key>
+    <dict>
+        <key>UIColorName</key>
+        <string></string>
+    </dict>
     <key>UISupportsDocumentBrowser</key>
     <false/>
     <key>UIRequiredDeviceCapabilities</key>