fix: agent-08 Kiosk-Härtung + 24h-Zeiteintrag-Bug

- fix: worked_minutes nutzt jetzt Sekunden statt Minuten für Overnight-Vergleich
  (end < start statt end <= start) – verhindert 24h-Anzeige bei Schnell-Stempel
  in derselben Minute (z.B. 23:34:46 → 23:34:48)
- fix: _check_arbzg() gleicher Sec-basierter Fix
- fix: KioskDeviceStatus Enum values_callable → kiosk list crasht nicht mehr
- feat: kiosk rotate-key CLI-Kommando (Status→pending, Re-Enrollment)
- feat: Kiosk-Settings in CompanyOut/CompanyUpdate Schema (require_approval,
  track_current_user, heartbeat_interval_sec)
- feat: Kiosk-Terminal-Einstellungsblock in CompanySettingsPage (🖥️)

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

backend/app/services/time_service.py

@@ -19,11 +19,11 @@ from app.schemas.time_entry import (
 
 def _check_arbzg(start: time, end: time, break_minutes: int) -> list[str]:
     """ArbZG §3 und §4 Prüfung. Gibt Warnungen zurück, blockiert nicht."""
-    start_mins = start.hour * 60 + start.minute
-    end_mins = end.hour * 60 + end.minute
-    if end_mins <= start_mins:
-        end_mins += 24 * 60  # Nachtschicht
-    total_mins = end_mins - start_mins
+    start_secs = start.hour * 3600 + start.minute * 60 + start.second
+    end_secs = end.hour * 3600 + end.minute * 60 + end.second
+    if end_secs < start_secs:
+        end_secs += 24 * 3600  # Nachtschicht
+    total_mins = (end_secs - start_secs) // 60
     worked_mins = total_mins - break_minutes
     worked_hours = worked_mins / 60