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/calendar_sync_api_step.py

@@ -0,0 +1,112 @@
+"""
+Calendar Sync API Step
+
+HTTP API endpoint for manual calendar sync triggering.
+Supports syncing a single employee or all employees.
+"""
+import sys
+from pathlib import Path
+sys.path.insert(0, str(Path(__file__).parent))
+from calendar_sync_utils import get_redis_client, set_employee_lock, log_operation
+
+from motia import http, ApiRequest, ApiResponse, FlowContext
+
+
+config = {
+    'name': 'Calendar Sync API Trigger',
+    'description': 'API endpoint for manual calendar sync triggering',
+    'flows': ['advoware'],
+    'triggers': [
+        http('POST', '/advoware/calendar/sync')
+    ],
+    'enqueues': ['calendar_sync_employee', 'calendar_sync_all']
+}
+
+
+async def handler(request: ApiRequest, ctx: FlowContext) -> ApiResponse:
+    """
+    HTTP handler for manual calendar sync triggering.
+    
+    Request body:
+        {
+            "kuerzel": "SB"  // or "ALL" for all employees
+        }
+    """
+    try:
+        # Get kuerzel from request body
+        body = request.body
+        kuerzel = body.get('kuerzel')
+        if not kuerzel:
+            return ApiResponse(
+                status=400,
+                body={
+                    'error': 'kuerzel required',
+                    'message': 'Bitte kuerzel im Body angeben'
+                }
+            )
+
+        kuerzel_upper = kuerzel.upper()
+
+        if kuerzel_upper == 'ALL':
+            # Emit sync-all event
+            log_operation('info', "Calendar Sync API: Emitting sync-all event", context=ctx)
+            await ctx.enqueue({
+                "topic": "calendar_sync_all",
+                "data": {
+                    "triggered_by": "api"
+                }
+            })
+            return ApiResponse(
+                status=200,
+                body={
+                    'status': 'triggered',
+                    'message': 'Calendar sync wurde für alle Mitarbeiter ausgelöst',
+                    'triggered_by': 'api'
+                }
+            )
+        else:
+            # Single employee sync
+            redis_client = get_redis_client(ctx)
+            
+            if not set_employee_lock(redis_client, kuerzel_upper, 'api', ctx):
+                log_operation('info', f"Calendar Sync API: Sync already active for {kuerzel_upper}, skipping", context=ctx)
+                return ApiResponse(
+                    status=409,
+                    body={
+                        'status': 'conflict',
+                        'message': f'Calendar sync already active for {kuerzel_upper}',
+                        'kuerzel': kuerzel_upper,
+                        'triggered_by': 'api'
+                    }
+                )
+
+            log_operation('info', f"Calendar Sync API called for {kuerzel_upper}", context=ctx)
+            
+            # Lock successfully set, now emit event
+            await ctx.enqueue({
+                "topic": "calendar_sync_employee",
+                "data": {
+                    "kuerzel": kuerzel_upper,
+                    "triggered_by": "api"
+                }
+            })
+
+            return ApiResponse(
+                status=200,
+                body={
+                    'status': 'triggered',
+                    'message': f'Calendar sync was triggered for {kuerzel_upper}',
+                    'kuerzel': kuerzel_upper,
+                    'triggered_by': 'api'
+                }
+            )
+
+    except Exception as e:
+        log_operation('error', f"Error in API trigger: {e}", context=ctx)
+        return ApiResponse(
+            status=500,
+            body={
+                'error': 'Internal server error',
+                'details': str(e)
+            }
+        )