Improve query performance using explicit INDEXED BY (#3550)

app/sql.js

@@ -2233,6 +2233,7 @@ async function getExpiredMessages() {
 async function getOutgoingWithoutExpiresAt() {
   const rows = await db.all(`
     SELECT json FROM messages
+    INDEXED BY messages_without_timer
     WHERE
       expireTimer > 0 AND
       expires_at IS NULL AND