Fix Monday.com webhook subscription and improve API client

- Add API-Version header to all Monday.com GraphQL requests
- Switch create_webhook/delete_webhook to inline values matching Monday's
  documented syntax (fixes Internal Server Error on subscribe)
- Add extended error details from Monday.com GraphQL responses

Made-with: Cursor

src/lib/monday.ts

@@ -9,6 +9,7 @@ async function gql(token: string, query: string, variables?: Record<string, unkn
     headers: {
       "Content-Type": "application/json",
       Authorization: token,
+      "API-Version": "2024-10",
     },
     body: JSON.stringify({ query, variables }),
   });
@@ -18,7 +19,12 @@ async function gql(token: string, query: string, variables?: Record<string, unkn
   }
   const json = await res.json();
   if (json.errors?.length) {
-    throw new Error(`Monday.com GraphQL: ${json.errors[0].message}`);
+    const err = json.errors[0];
+    const detail = err.extensions ? ` (${JSON.stringify(err.extensions)})` : "";
+    throw new Error(`Monday.com GraphQL: ${err.message}${detail}`);
+  }
+  if (json.error_message) {
+    throw new Error(`Monday.com: ${json.error_message}`);
   }
   return json.data;
 }
@@ -169,11 +175,15 @@ export async function createWebhookSubscription(
   boardId: string,
   callbackUrl: string
 ): Promise<string> {
+  const escapedUrl = callbackUrl.replace(/\\/g, "\\\\").replace(/"/g, '\\"');
   const data = await gql(token, `
-    mutation ($boardId: ID!, $url: String!) {
-      create_webhook(board_id: $boardId, url: $url, event: change_column_value) { id }
+    mutation {
+      create_webhook(board_id: ${boardId}, url: "${escapedUrl}", event: change_column_value) {
+        id
+        board_id
       }
-  `, { boardId, url: callbackUrl });
+    }
+  `);
   return String(data.create_webhook.id);
 }
 
@@ -182,8 +192,10 @@ export async function deleteWebhookSubscription(
   webhookId: string
 ): Promise<void> {
   await gql(token, `
-    mutation ($webhookId: ID!) {
-      delete_webhook(id: $webhookId) { id }
+    mutation {
+      delete_webhook(id: ${webhookId}) {
+        id
       }
-  `, { webhookId });
+    }
+  `);
 }