Add base model and specific implementations for Vae, Lora, and Checkpoint; introduce exception handling and event types

lib/src/models/lora.dart

@@ -0,0 +1,13 @@
+import 'base_model.dart';
+
+class Lora extends BaseModel {
+  Lora({required String name, required int pathIndex})
+      : super(name: name, pathIndex: pathIndex);
+
+  factory Lora.fromJson(Map<String, dynamic> json) {
+    return Lora(
+      name: json['name'] as String,
+      pathIndex: json['pathIndex'] as int,
+    );
+  }
+}