Add the App Store link to the friend invite message

CLAUDE.md

@@ -88,7 +88,7 @@ Fully implemented end-to-end.
 
 ## Tests
 
-- `test/widget_test.dart` uses `firebase_auth_mocks` + `fake_cloud_firestore` and `setupFirebaseCoreMocks()` — tests run without real Firebase. **707 Dart tests passing.**
+- `test/widget_test.dart` uses `firebase_auth_mocks` + `fake_cloud_firestore` and `setupFirebaseCoreMocks()` — tests run without real Firebase. **709 Dart tests passing.**
 - `functions/src/test/test.index.ts` uses `firebase-functions-test`. **606 TypeScript tests passing** (pure unit tests + auth/validation integration tests that gracefully skip when no emulator is running). Includes tests for `updateFcmTokens`, `diffFriends`, `shouldNotifyFirstClaim`, `shouldNotifyOvertake`, `buildOsmChange`, `parsePhotos`, `nextQuotaState`, `pointsForMonarch`, `maxDailyFromClaims`, `repointClaimsForPostbox` (mock Firestore), `submitReport`/`reviewReport` auth & validation, and the `plan_route` CLI helpers.
 - `test/cross_language_sync_test.dart` is the drift guard for facts duplicated across languages/files. Beyond the constants listed under "Added features", it now also parses source to assert: every `startScoring` call site sends an `attemptId` (Dart sheet, Wear, **and the Kotlin car**); every claim surface consults `MaintenanceGuard` and every entry point initialises Remote Config; and every collection the Cloud Functions touch has a `match` block in `firestore.rules`. Each is verified to FAIL when the thing it guards is removed. `countySlug` is checked against all 218 features of the heatmap geojson (TS side, `test.index.ts`).
 

lib/friends_screen.dart

@@ -2,7 +2,8 @@ import 'dart:async';
 
 import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:firebase_auth/firebase_auth.dart';
-import 'package:flutter/foundation.dart' show setEquals;
+import 'package:flutter/foundation.dart'
+    show TargetPlatform, defaultTargetPlatform, setEquals;
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:postbox_game/analytics_service.dart';
@@ -21,13 +22,24 @@ import 'package:share_plus/share_plus.dart';
 const String _playStoreUrl =
     'https://play.google.com/store/apps/details?id=com.code418.postbox_game';
 
+/// App Store listing, from the app's Apple ID in App Store Connect.
+const String _appStoreUrl = 'https://apps.apple.com/app/id6819213888';
+
 /// Builds the invite message shared via the OS share sheet. Includes the
 /// user's UID so the recipient can add them back as a friend.
-String buildInviteMessage(String uid) =>
-    "Join me on Postbox Game! Hunt down Britain's historic postboxes, "
-    'claim them for points and climb the leaderboards.\n\n'
-    'Add me as a friend with my UID: $uid\n\n'
-    '$_playStoreUrl';
+///
+/// The recipient's phone is unknown, so both store links are included,
+/// labelled. The sender's own store comes first ([platform], defaulting to
+/// this device), since friends tend to share a platform.
+String buildInviteMessage(String uid, {TargetPlatform? platform}) {
+  final ios = (platform ?? defaultTargetPlatform) == TargetPlatform.iOS;
+  const iphone = 'iPhone: $_appStoreUrl';
+  const android = 'Android: $_playStoreUrl';
+  return "Join me on Postbox Game! Hunt down Britain's historic postboxes, "
+      'claim them for points and climb the leaderboards.\n\n'
+      'Add me as a friend with my UID: $uid\n\n'
+      '${ios ? '$iphone\n$android' : '$android\n$iphone'}';
+}
 
 /// Friends list and add-friend by UID.
 /// Display names learned from one batched `users` lookup of [batch], given

test/widget_test.dart

@@ -1012,6 +1012,23 @@ void main() {
     test('uses no em-dash, matching the app writing voice', () {
       expect(buildInviteMessage('abc123'), isNot(contains('—')));
     });
+
+    test('includes the App Store link too, whatever the sender uses', () {
+      for (final platform in [TargetPlatform.android, TargetPlatform.iOS]) {
+        expect(buildInviteMessage('abc123', platform: platform),
+            contains('https://apps.apple.com/app/id6819213888'),
+            reason: '$platform');
+      }
+    });
+
+    test("lists the sender's own store first", () {
+      int at(String msg, String s) => msg.indexOf(s);
+      final fromIos = buildInviteMessage('abc123', platform: TargetPlatform.iOS);
+      expect(at(fromIos, 'iPhone:'), lessThan(at(fromIos, 'Android:')));
+      final fromAndroid =
+          buildInviteMessage('abc123', platform: TargetPlatform.android);
+      expect(at(fromAndroid, 'Android:'), lessThan(at(fromAndroid, 'iPhone:')));
+    });
   });
 
   // ---------------------------------------------------------------------------