Billing Stripe, link regia mobile e staff solo trasmissione.

Aggiunge fatturazione club, pagina regia condivisibile senza account, roster squadre e rimuove la modalità controller dall'app (v1.1.0).

Co-authored-by: Cursor <cursoragent@cursor.com>

mobile/lib/core/team_selection_storage.dart

@@ -0,0 +1,22 @@
+import 'package:shared_preferences/shared_preferences.dart';
+
+class TeamSelectionStorage {
+  static const _keySelectedTeamId = 'selected_team_id';
+
+  static Future<String?> load() async {
+    final prefs = await SharedPreferences.getInstance();
+    final id = prefs.getString(_keySelectedTeamId);
+    if (id == null || id.isEmpty) return null;
+    return id;
+  }
+
+  static Future<void> save(String teamId) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setString(_keySelectedTeamId, teamId);
+  }
+
+  static Future<void> clear() async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.remove(_keySelectedTeamId);
+  }
+}