fix(ios): bump react-native-skia to 2.6.9 for the base64 header fix

2.6.2 fails to archive under the SDK 56 toolchain: base64.cpp includes
third_party/base64.h, which the podspec header glob no longer resolves.
2.6.9 includes the header relative to its own directory.

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

apps/mobile/package.json

@@ -44,7 +44,7 @@
     "@react-native-firebase/app": "^23.8.2",
     "@react-native-firebase/crashlytics": "^23.8.4",
     "@react-native-google-signin/google-signin": "^16.1.1",
-    "@shopify/react-native-skia": "2.6.2",
+    "@shopify/react-native-skia": "^2.6.9",
     "@supabase/supabase-js": "^2.39.0",
     "@tanstack/react-query": "^5.17.0",
     "babel-preset-expo": "~56.0.0",