feat: filter webhooks per project, board, and account

Adds optional project, board, and acting-user scope to each webhook so
events from a specific board or project can be routed to a single
endpoint without an external automation tool in the middle (closes
#1457).

A webhook now fires for an event only when every set scope matches:
empty scope still means "fire for everything", keeping existing
webhooks working unchanged. Scope filtering is centralized in the
sendWebhooks helper, which auto-derives projectId/boardId from the
event payload, so existing call sites are untouched.

client/src/components/common/AdministrationModal/WebhooksPane.jsx

@@ -15,6 +15,9 @@ import styles from './WebhooksPane.module.scss';
 
 const WebhooksPane = React.memo(() => {
   const webhookIds = useSelector(selectors.selectWebhookIds);
+  const projects = useSelector(selectors.selectProjects);
+  const boards = useSelector(selectors.selectBoards);
+  const users = useSelector(selectors.selectUsers);
 
   const dispatch = useDispatch();
 
@@ -27,7 +30,13 @@ const WebhooksPane = React.memo(() => {
 
   return (
     <Tab.Pane attached={false} className={styles.wrapper}>
-      <Webhooks ids={webhookIds} onCreate={handleCreate} />
+      <Webhooks
+        ids={webhookIds}
+        projects={projects}
+        boards={boards}
+        users={users}
+        onCreate={handleCreate}
+      />
     </Tab.Pane>
   );
 });