Bring the phone app's analyzer up to latest stable

very_good_analysis ^10.3.0 -> ^11.0.0, which the freshness gate flagged
against phone_app/pubspec.yaml the moment the pre-push CI mirror ran
--all-files. Pre-existing; it blocked the push rather than being caused
by it.

The major bump newly flags two async_return_with_no_await sites, both now
`return await` rather than suppressed. The rule is correct in both: a
future returned without awaiting escapes the enclosing async function, so
a failure surfaces at the caller with a stack trace that no longer names
the code that made the call. firebase_backend.dart:91 is the one that
matters -- a rejected credential fetch should fail inside the function
that describes itself as recovering from exactly that.

flutter analyze clean, 146 phone-app tests pass.

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

phone_app/lib/services/firebase_backend.dart

@@ -88,7 +88,7 @@ Future<FirebaseRestClient?> openFirebase() async {
     // marker beside it. Treating the marker as the source of truth is what
     // made a phone with a live session sync over GitHub and 401 forever --
     // the credential was in the keystore the whole time, unused.
-    return _clientFromStoredSession();
+    return await _clientFromStoredSession();
   }
   try {
     return await firebaseClientFor(

phone_app/lib/services/google_sign_in_backend.dart

@@ -75,7 +75,7 @@ Future<String?> googleIdToken({
   Future<String?> Function()? signInFn,
   String serverClientId = kServerClientId,
 }) async {
-  if (signInFn != null) return signInFn();
+  if (signInFn != null) return await signInFn();
   if (serverClientId.isEmpty) {
     // A build without --dart-define=GOOGLE_SERVER_CLIENT_ID would otherwise
     // fail inside the plugin with a far less obvious message.

phone_app/pubspec.lock

@@ -724,10 +724,10 @@ packages:
     dependency: "direct dev"
     description:
       name: very_good_analysis
-      sha256: "481af67ab5877af20325251dc215a4ebac7666a1c8cf09198ffd457bc612b33d"
+      sha256: "0bd5eb8d6be76aa0d71e70cbdae6cac8f784f761170568e3c2214a6948c7f6d3"
       url: "https://pub.dev"
     source: hosted
-    version: "10.3.0"
+    version: "11.0.0"
   vm_service:
     dependency: transitive
     description:
@@ -777,5 +777,5 @@ packages:
     source: hosted
     version: "3.1.3"
 sdks:
-  dart: ">=3.12.2 <4.0.0"
+  dart: ">=3.13.0 <4.0.0"
   flutter: ">=3.44.0"

phone_app/pubspec.yaml

@@ -49,7 +49,7 @@ dev_dependencies:
   flutter_launcher_icons: 0.14.4
   flutter_test:
     sdk: flutter
-  very_good_analysis: ^10.3.0
+  very_good_analysis: ^11.0.0
 
 flutter:
   uses-material-design: true