fix(app): toon API-fout bij opnieuw toewijzen shift in snackbar

Made-with: Cursor

apps/app/src/lib/apiErrors.ts

@@ -0,0 +1,26 @@
+import { isAxiosError } from 'axios'
+
+/**
+ * Human-readable message from Laravel API validation / exception responses.
+ */
+export function getApiErrorMessage(error: unknown, fallback: string): string {
+  if (!isAxiosError(error)) return fallback
+
+  const data = error.response?.data as Record<string, unknown> | undefined
+  if (!data) return fallback
+
+  const errors = data.errors
+  if (errors && typeof errors === 'object' && errors !== null && !Array.isArray(errors)) {
+    for (const value of Object.values(errors as Record<string, unknown>)) {
+      if (Array.isArray(value) && value.length > 0 && typeof value[0] === 'string')
+        return value[0]
+
+      if (typeof value === 'string') return value
+    }
+  }
+
+  const message = data.message
+  if (typeof message === 'string' && message.trim() !== '') return message
+
+  return fallback
+}