Beta 2. Fixes a first-run baseline bug found during beta1 testing: the container's mysql/clickhouse UIDs are assigned dynamically by apt at image build time (mysql GID=101 on current build, clickhouse UID=995), so hardcoded migration defaults would produce an incorrect baseline. Now reads actual UIDs via id -u at startup. Pull with marcpope/borgbackupserver:v2.27.0-beta2.