fix templates v2

internal/db/db.go

@@ -218,6 +218,9 @@ func ensureFrequentlyUsedIndexes(db *gorm.DB) error {
 	indexes := []string{
 		`CREATE INDEX IF NOT EXISTS idx_questions_asker_user_id ON questions(asker_user_id)`,
 		`CREATE INDEX IF NOT EXISTS idx_questions_user_private_created ON questions(user_id, is_private, created_at)`,
+		// 「下一条未读」：user_id + is_read 过滤后按 created_at 取最早一条。
+		// 上面那条中间隔着 is_private，帮不上这个排序。
+		`CREATE INDEX IF NOT EXISTS idx_questions_user_unread_created ON questions(user_id, is_read, created_at)`,
 		`CREATE INDEX IF NOT EXISTS idx_users_show_in_home_created ON users(show_in_home, created_at)`,
 		`CREATE INDEX IF NOT EXISTS idx_votes_status_visibility_created ON votes(status, visibility, created_at)`,
 		`CREATE INDEX IF NOT EXISTS idx_messages_sender_created ON messages(sender_id, created_at)`,