look aheead limit defined by user

lib/services/storage_service.dart

@@ -122,6 +122,17 @@ class StorageService {
     return _prefs.setString(StorageKeys.themeMode, value);
   }
 
+  /// Look ahead navigation horizon in years (clamped 1–30, default 5).
+  int get lookAheadMaxYears {
+    final raw = _prefs.getInt(StorageKeys.lookAheadMaxYears);
+    if (raw == null) return 5;
+    return raw.clamp(1, 30);
+  }
+
+  Future<void> setLookAheadMaxYears(int years) {
+    return _prefs.setInt(StorageKeys.lookAheadMaxYears, years.clamp(1, 30));
+  }
+
   bool get useRemoteData => _prefs.getBool(StorageKeys.useRemoteData) ?? false;
 
   Future<void> setUseRemoteData(bool value) {