fixes, improvements, and cleanup. notably, custom camera profiles make a comeback.

lib/services/profile_service.dart

@@ -0,0 +1,29 @@
+import 'dart:convert';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import '../models/camera_profile.dart';
+
+class ProfileService {
+  static const _key = 'custom_profiles';
+
+  Future<List<CameraProfile>> load() async {
+    final prefs = await SharedPreferences.getInstance();
+    final jsonStr = prefs.getString(_key);
+    if (jsonStr == null) return [];
+    final list = jsonDecode(jsonStr) as List<dynamic>;
+    return list.map((e) => CameraProfile.fromJson(e)).toList();
+  }
+
+  Future<void> save(List<CameraProfile> profiles) async {
+    final prefs = await SharedPreferences.getInstance();
+
+    // MUST convert to List before jsonEncode; the previous MappedIterable
+    // caused "Converting object to an encodable object failed".
+    final encodable = profiles
+        .where((p) => !p.builtin)
+        .map((p) => p.toJson())
+        .toList(); // <- crucial
+
+    await prefs.setString(_key, jsonEncode(encodable));
+  }
+}