feat(webhooks): add per-verb subscriptions and bulk-create debounce

Subscriptions now declare a `verb` (create | delete | bulk-create).
POST /:did/webhooks defaults to inserting both create and delete rows
when no verb is given, preserving existing all-events behavior. Update
events fold into the create verb. The new bulk-create verb debounces
creates per DID over 400 ms and delivers a `records` array.

Migration adds the verb column with default 'create' and clones every
existing row for the delete verb so legacy subscriptions keep firing
on both events.

src/data/db.ts

@@ -87,26 +87,30 @@ export const saveCursor = (cursor: number) => {
   );
 };
 
+export type WebhookVerb = "create" | "delete" | "bulk-create";
+
 type WebhookSubscriptionRow = {
   id: number;
   did: string;
   method: string;
   url: string;
   token?: string;
+  verb: WebhookVerb;
 };
 
 export const addWebhookSubscription = (
-  { did, method, url, token }: Omit<WebhookSubscriptionRow, "id">,
+  { did, method, url, token, verb }: Omit<WebhookSubscriptionRow, "id">,
 ): WebhookSubscriptionRow => {
   db.exec(
-    "INSERT INTO webhook_subscription (did, method, url, token) VALUES (?, ?, ?, ?)",
+    "INSERT INTO webhook_subscription (did, method, url, token, verb) VALUES (?, ?, ?, ?, ?)",
     did,
     method,
     url,
     token ?? null,
+    verb,
   );
   return db.prepare(
-    "SELECT id, did, method, url FROM webhook_subscription WHERE id = last_insert_rowid()",
+    "SELECT id, did, method, url, verb FROM webhook_subscription WHERE id = last_insert_rowid()",
   ).get<WebhookSubscriptionRow>()!;
   // Note: token is intentionally excluded from the SELECT (write-only)
 };
@@ -115,10 +119,13 @@ export const deleteWebhooksByDid = (did: string): void => {
   db.exec("DELETE FROM webhook_subscription WHERE did = ?", did);
 };
 
-export const getWebhooksByDid = (did: string): WebhookSubscriptionRow[] => {
+export const getWebhooksByDidAndVerb = (
+  did: string,
+  verb: WebhookVerb,
+): WebhookSubscriptionRow[] => {
   return db.prepare(
-    "SELECT id, did, method, url, token FROM webhook_subscription WHERE did = ? ORDER BY id DESC LIMIT 10",
-  ).all<WebhookSubscriptionRow>(did);
+    "SELECT id, did, method, url, token, verb FROM webhook_subscription WHERE did = ? AND verb = ? ORDER BY id DESC LIMIT 10",
+  ).all<WebhookSubscriptionRow>(did, verb);
 };
 
 export const upsertNote = (note: Note) => {

src/migrations/init.ts

@@ -61,4 +61,23 @@ try {
   // Column already exists — no-op
 }
 
+try {
+  db.exec(
+    `ALTER TABLE webhook_subscription ADD COLUMN verb TEXT NOT NULL DEFAULT 'create';`,
+  );
+  db.exec(`
+    INSERT INTO webhook_subscription (did, method, url, token, verb)
+    SELECT did, method, url, token, 'delete'
+    FROM webhook_subscription
+    WHERE verb = 'create';
+  `);
+} catch {
+  // Column already exists — backfill already happened on a previous run.
+}
+
+db.exec(`
+  CREATE INDEX IF NOT EXISTS idx_webhook_subscription_did_verb
+    ON webhook_subscription(did, verb);
+`);
+
 db.close();