Add calendar sync utilities and Beteiligte sync cron job

- Implemented calendar_sync_utils.py for shared utility functions
  including DB connection, Google Calendar service initialization,
  Redis client setup, and employee sync operations.

- Created beteiligte_sync_cron_step.py to handle periodic sync
  of Beteiligte entities, checking for new, modified, failed,
  and stale records, and emitting sync events accordingly.

steps/advoware_cal_sync/__init__.py

@@ -0,0 +1,5 @@
+"""
+Advoware Calendar Sync Module
+
+Bidirectional synchronization between Google Calendar and Advoware appointments.
+"""