The SQLite panel's Restore now detects the upload by content like the
PostgreSQL panel does: migration dumps are rebuilt with RestoreSQLite,
pg_dump archives get a clear error instead of 'Invalid db file format',
and every upload passes the panel-schema pre-flight before Xray stops.
The .backup fallback survives a failed Xray start and is named in the
error, the DB pool is reopened on every error path after CloseDB, and a
failed InitDB closes the imported file before restoring the fallback so
the rename cannot hit a Windows sharing violation.
MHSanaei