feat(hosts): generate unique 8-digit asset ID

Add a Generate button to the host create dialog that fetches a random
8-digit asset ID from the new GET /hosts/generate-asset-id endpoint.
The service retries against the unique index so the returned ID is
guaranteed unused. Edit mode hides the button.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/lib/api/hosts.ts

@@ -42,3 +42,8 @@ export async function updateHost(id: string, input: UpdateHostRequest): Promise<
 export async function deleteHost(id: string): Promise<void> {
   await api.delete(`/hosts/${id}`);
 }
+
+export async function generateHostAssetId(): Promise<{ assetId: string }> {
+  const res = await api.get<{ assetId: string }>('/hosts/generate-asset-id');
+  return res.data;
+}