fix(database): create SQLite backup snapshots online (#6137)

* fix(database): snapshot SQLite backups online

Use SQLite's online backup API for downloadable backups and SQLite migration exports instead of checkpointing then reading the live database file. The regression test validates a backup made while writes continue.

* style(database): group SQLite driver imports

* fix(database): bound online backup retries

Use a single backup step and a bounded connection-acquisition/retry context. Tighten temporary-file cleanup and regression assertions while removing the unused checkpoint helper.

* test(database): cover existing backup destinations

* fix(database): harden SQLite snapshot lifecycle

Sweep interrupted snapshot directories at SQLite startup, keep rollback-journal backups incremental, and make caller-owned cleanup explicit. Reuse one scheduled Telegram snapshot across administrators and make the direct SQLite driver dependency explicit.

---------

Co-authored-by: PathGao <gaoyanbo@gaoyanbodeMacBook-Air.local>

internal/web/service/server.go

@@ -1303,25 +1303,26 @@ func (s *ServerService) GetDb() ([]byte, error) {
 	if database.IsPostgres() {
 		return s.exportPostgresDB()
 	}
-	// Update by manually trigger a checkpoint operation
-	err := database.Checkpoint()
+	backupPath, cleanup, err := s.backupSQLite()
 	if err != nil {
 		return nil, err
 	}
-	// Open the file for reading
-	file, err := os.Open(config.GetDBPath())
-	if err != nil {
-		return nil, err
-	}
-	defer file.Close()
+	defer cleanup()
+	return os.ReadFile(backupPath)
+}
 
-	// Read the file contents
-	fileContents, err := io.ReadAll(file)
+func (s *ServerService) backupSQLite() (string, func(), error) {
+	backupDir, err := os.MkdirTemp(filepath.Dir(config.GetDBPath()), ".x-ui-backup-")
 	if err != nil {
-		return nil, err
+		return "", nil, err
 	}
-
-	return fileContents, nil
+	cleanup := func() { _ = os.RemoveAll(backupDir) }
+	backupPath := filepath.Join(backupDir, "backup.db")
+	if err := database.BackupSQLite(backupPath); err != nil {
+		cleanup()
+		return "", nil, err
+	}
+	return backupPath, cleanup, nil
 }
 
 // BackupFilename returns the filename for a database backup, named after the
@@ -1421,11 +1422,12 @@ func (s *ServerService) GetMigration() ([]byte, string, error) {
 		return data, "x-ui.db", nil
 	}
 
-	// SQLite panel: checkpoint so the .db reflects the latest writes, then dump.
-	if err := database.Checkpoint(); err != nil {
+	backupPath, cleanup, err := s.backupSQLite()
+	if err != nil {
 		return nil, "", err
 	}
-	data, err := database.DumpSQLiteToBytes(config.GetDBPath())
+	defer cleanup()
+	data, err := database.DumpSQLiteToBytes(backupPath)
 	if err != nil {
 		return nil, "", err
 	}