task(F1-frontend): library export/import buttons in block library tree

frontend/src/services/api.ts

@@ -812,3 +812,33 @@ export async function deleteGuest(token: string, id: string): Promise<void> {
   });
   if (!res.ok) throw new Error(`Failed to delete guest: ${res.status}`);
 }
+
+// ─── Library Paket Export/Import (Task F1) ─────────────
+export interface WcadlibPackage {
+  format: 'wcadlib';
+  version: number;
+  exported_at?: string;
+  folders: Array<{ id: string; name: string; parent_id: string | null }>;
+  blocks: Array<{ name: string; folder_id: string | null; block_data: string; svg_data: string | null }>;
+}
+
+export async function exportLibrary(token: string): Promise<unknown> {
+  const res = await fetch(`${API_BASE}/api/global-blocks/export`, {
+    headers: authHeaders(token),
+  });
+  if (!res.ok) throw new Error(`Failed to export library: ${res.status}`);
+  return res.json();
+}
+
+export async function importLibrary(token: string, pkg: { format: string; version?: number; folders?: Array<{ id: string; name: string; parent_id: string | null }>; blocks: Array<{ name: string; folder_id: string | null; block_data: string; svg_data: string | null }> }): Promise<{ imported_blocks: number; imported_folders: number }> {
+  const res = await fetch(`${API_BASE}/api/global-blocks/import`, {
+    method: 'POST',
+    headers: authHeaders(token),
+    body: JSON.stringify(pkg),
+  });
+  if (!res.ok) {
+    const err = await res.text();
+    throw new Error(`Failed to import library: ${res.status} ${err}`);
+  }
+  return res.json();
+}