feat: fire webhooks on jetstream events, cap at 10 per DID

- db.ts: getWebhooksByDid returns the 10 most recent subscriptions (ORDER BY id DESC LIMIT 10)
- jetstream.ts: fireWebhooks fans out to registered URLs via Promise.allSettled after each create/update/delete event

src/data/db.ts

@@ -92,6 +92,12 @@ export const deleteWebhooksByDid = (did: string): void => {
   db.exec("DELETE FROM webhook_subscription WHERE did = ?", did);
 };
 
+export const getWebhooksByDid = (did: string): WebhookSubscriptionRow[] => {
+  return db.prepare(
+    "SELECT id, did, method, url FROM webhook_subscription WHERE did = ? ORDER BY id DESC LIMIT 10",
+  ).all<WebhookSubscriptionRow>(did);
+};
+
 export const upsertNote = (note: Note) => {
   const now = new Date().toISOString();
   db.exec(