fix(ios): weak-link SwiftUICore on app target to bypass Xcode 26 autolink error

Build #8 confirmed BOTH iOS jobs (signed + unsigned) fail at the same step:
the Streamyfin app-target link (`Ld ... Streamyfin`), not any pod framework.
Under use_frameworks static + Xcode 26 the SwiftUI pods' object files carry a
`-framework SwiftUICore` autolink directive that flows into the app link; ld
rejects it with "cannot link directly with 'SwiftUICore' because product being
built is not an allowed client of it".

forceStaticLinking the SwiftUI pods was treating a symptom. The real fix is to
weakly link SwiftUICore on the app target so the allowed-client check is
bypassed and the symbols resolve via SwiftUI's re-export at runtime.

New plugin withSwiftUICoreWeakLink scopes the flag to product-type application
only, leaving the tvOS TopShelf app-extension untouched (a broad weak-link
previously broke that target).

app.json

@@ -133,6 +133,7 @@
       ],
       "expo-web-browser",
       ["./plugins/with-runtime-framework-headers.js"],
+      ["./plugins/withSwiftUICoreWeakLink.js"],
       ["./plugins/withChangeNativeAndroidTextToWhite.js"],
       ["./plugins/withAndroidAlertColors.js"],
       ["./plugins/withAndroidManifest.js"],