fix(ios): App Store validation — strip 1024 alpha + drop iCloud entitlements

Apple's TestFlight upload validator rejected v2.5 with two errors;
fixing both for the next archive.

1. **Invalid large app icon** (alpha channel).
   `AppIcon.appiconset/AW Mac OS Applications-macOS-Default-1024x1024@1x.png`
   was RGBA — Apple rejects any 1024×1024 marketing icon with an alpha
   channel. Composited the icon onto a solid white background via
   PIL and resaved as RGB PNG. `sips -g hasAlpha` now reports `no`.
   The file's design is solid edge-to-edge, so the white-fill is
   invisible — no visual change.

2. **Invalid Code Signing Entitlements**
   (`com.apple.developer.icloud-container-environment` empty string).
   `Scarf_iOS.entitlements` had `com.apple.developer.icloud-services
   = [CloudKit]` + `com.apple.developer.icloud-container-identifiers
   = []`. Xcode's signing phase synthesises
   `com.apple.developer.icloud-container-environment` from this combo,
   and with no container identifier the value lands as empty — which
   Apple's validator rejects.

   Per the privacy policy I drafted in v2.5 ("no iCloud Keychain
   sync, no cloud accounts") Scarf doesn't actually use iCloud, so
   removing the iCloud entries is the correct fix. Dropped both
   `com.apple.developer.icloud-services` and
   `com.apple.developer.icloud-container-identifiers`. Kept
   `aps-environment = development` — push capability stays declared
   but gated off via `NotificationRouter.apnsEnabled = false` until
   the cert + Hermes-side sender land.

iOS scheme builds clean post-fix.

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

scarf/Scarf iOS/Scarf_iOS.entitlements

@@ -4,11 +4,5 @@
 <dict>
 	<key>aps-environment</key>
 	<string>development</string>
-	<key>com.apple.developer.icloud-container-identifiers</key>
-	<array/>
-	<key>com.apple.developer.icloud-services</key>
-	<array>
-		<string>CloudKit</string>
-	</array>
 </dict>
 </plist>