feat: add form-io module for JSON export/import

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/utils/form-io.ts

@@ -0,0 +1,54 @@
+import { FormDefinition } from '../types';
+
+interface FormExport {
+  version: 1;
+  forms: FormDefinition[];
+}
+
+/**
+ * Serialize forms to a JSON string with a version wrapper.
+ */
+export function exportForms(forms: FormDefinition[]): string {
+  const payload: FormExport = { version: 1, forms };
+  return JSON.stringify(payload, null, 2);
+}
+
+/**
+ * Parse a JSON string and extract valid FormDefinitions.
+ * Generates new UUIDs for each imported form to prevent ID collisions.
+ * Throws on invalid input.
+ */
+export function importForms(json: string): FormDefinition[] {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(json);
+  } catch {
+    throw new Error('Invalid JSON file');
+  }
+
+  if (
+    typeof parsed !== 'object' ||
+    parsed === null ||
+    !('forms' in parsed) ||
+    !Array.isArray((parsed as FormExport).forms)
+  ) {
+    throw new Error('Invalid form format: missing "forms" array');
+  }
+
+  const rawForms = (parsed as FormExport).forms;
+
+  for (const form of rawForms) {
+    if (!form.name || !Array.isArray(form.fields)) {
+      throw new Error(
+        'Invalid form format: each form needs "name" and "fields"',
+      );
+    }
+  }
+
+  // Generate fresh IDs to avoid collisions
+  return rawForms.map((form) => ({
+    ...form,
+    id: crypto.randomUUID(),
+    name: form.name,
+  }));
+}