feat(apple/M1): PunktfunkWidgetsExtension target — wired, signed, building

The Xcode widget-extension target that hosts the launcher widget + Live Activity
UI. Bundle id io.unom.punktfunk.widgets, iOS 17, App Group group.io.unom.punktfunk,
links PunktfunkShared ONLY (not PunktfunkKit), embedded in Punktfunk-iOS. Sources
come from the PunktfunkWidgets/ synchronized folder. Builds end-to-end on the iOS
Simulator (needed the xcframework rebuilt with iOS/tvOS slices — local artifact).

- project.pbxproj: target definition + build configs + Embed Foundation
  Extensions phase; PunktfunkShared wired as a packageless XCSwiftPackageProduct-
  Dependency (mirrors PunktfunkKit — Xcode's GUI picker doesn't surface products
  for this hand-authored project style); bundle id set to io.unom.punktfunk.widgets.
- PunktfunkWidgetsExtension.entitlements: App Group only.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/apple/PunktfunkWidgetsExtension.entitlements

@@ -1,5 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
-<dict/>
+<dict>
+	<key>com.apple.security.application-groups</key>
+	<array>
+		<string>group.io.unom.punktfunk</string>
+	</array>
+</dict>
 </plist>