feat: app icon (Icon Composer) + Xcode project settings for it

punktfunk_Logo.icon (Icon Composer 2.0) in App/, ASSETCATALOG_COMPILER_APPICON_NAME set.
Compiles with Xcode 27 beta's actool; Xcode 26.5's actool crashes on EVERY .icon file
(known regression, Apple FB20183399, expo/expo#46121) — build with the beta (or 26.4.1)
until a 26.x fix lands. The icon itself is fine.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Punktfunk.xcodeproj/xcshareddata/xcschemes/Punktfunk.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "2600"
+   LastUpgradeVersion = "2650"
    version = "1.7">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -28,10 +28,6 @@
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES"
       shouldAutocreateTestPlan = "YES">
-      <!-- Package tests (PunktfunkKitTests) run via `swift test`; to run them from Xcode
-           add them once via Edit Scheme → Test → + (Xcode persists the reference here). -->
-      <Testables>
-      </Testables>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"