improved performance and battery usage on older devices

test/api/cache_store_test.dart

@@ -0,0 +1,21 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/api/cache_store.dart';
+
+void main() {
+  group('CacheStore.parse', () {
+    test('splits the timestamp header from the payload', () {
+      final entry = CacheStore.parse('1700000000000\n{"a":"b\\nc"}');
+      expect(entry!.lastUpdate, 1700000000000);
+      expect(entry.json, '{"a":"b\\nc"}');
+    });
+
+    test('keeps newlines inside the payload', () {
+      expect(CacheStore.parse('1\nline1\nline2')!.json, 'line1\nline2');
+    });
+
+    test('rejects files without a valid header', () {
+      expect(CacheStore.parse('{"a":1}'), isNull);
+      expect(CacheStore.parse('abc\n{}'), isNull);
+    });
+  });
+}