feat(backup): 实例备份第1轮——独立备份库迁移、settings 仓库路径字段、备份进度事件

packages/app-lib/migrations/20261002030100_pending-backup-repository-cleanups.sql

@@ -0,0 +1,4 @@
+CREATE TABLE pending_backup_repository_cleanups (
+	path TEXT PRIMARY KEY,
+	created_at INTEGER NOT NULL
+);