feat: implement full backend API for Pantree Phase 1 MVP

src/utils/errors.js

@@ -0,0 +1,21 @@
+'use strict';
+
+/**
+ * Application-level error.
+ * status  — HTTP status code
+ * code    — machine-readable error code
+ * message — human-readable message
+ * extra   — optional additional fields merged into the response body
+ */
+class AppError extends Error {
+  constructor(status, code, message, extra = null) {
+    super(message);
+    this.name = 'AppError';
+    this.status = status;
+    this.code = code;
+    this.isAppError = true;
+    this.extra = extra;
+  }
+}
+
+module.exports = { AppError };