TIME Phase T2 Leitstand Import

This phase adds the NEW-only Leitstand source import layer on top of the T1 TIME foundation.

Included

source-specific import tables in TIME schema (ls_*)
NEW-only external JDBC configuration for Leitstand
source client for the provided SQL Server 2000 tables
startup sync runner, disabled by default
importer that:
- upserts Leitstand source rows into TIME.ls_*
- creates/updates canonical TIME.time_entry + DOC.doc_document roots from E_90716
- writes source links for time recording, person, and activity type
- updates TIME.time_sync_run and TIME.time_sync_state