agent-07 phase 2: fix test isolation + CSV import UI

- Fix conftest.py: commit after each request in override_get_db so
  preview_csv's rollback no longer wipes the shared registered_user
  (root cause of 401 cascade across test_user_import + test_personnel_number)
- Fix limiter.enabled=False in client fixture (blocks rate-limit 429)
- Fix user_import_service: allow reactivation when personnel number
  belongs to the same user being reactivated
- Fix test_personnel_number: use PATCH /companies/me (not /companies/{id})
  and add try/finally cleanup for personnel_number_required flag
- Frontend UsersPage: add CSV import modal with template download,
  preview/validation table, and guarded apply button

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

DEVLOG.md

@@ -547,3 +547,15 @@ Keine Commits in dieser Session.
 Keine Änderungen ermittelbar.
 
 ---
+## 2026-05-23 20:11 – 20:12 (0m)
+**Beschreibung:** Claude Code Session
+**Projekt:** timemaster
+
+### Commits
+- 39a0e37 .gitignore und DEVLOG aktualisieren
+
+### Geänderte Dateien
+- .gitignore |  4 ++++
+- DEVLOG.md  | 22 ++++++++++++++++++++++
+
+---