Add exponential backoff for Google API calls

- Use backoff library with 5s base, max 5 tries for HttpError 429/5xx
- Decorate Google functions: ensure_calendar, fetch_events, create/update/delete events
- Add backoff to requirements.txt

bitbylaw/requirements.txt

@@ -6,3 +6,4 @@ redis
 python-dotenv
 google-api-python-client
 google-auth
+backoff

bitbylaw/steps/advoware_cal_sync/calendar_sync_event_step.py

@@ -4,6 +4,7 @@ import os
 import datetime
 from datetime import timedelta
 import pytz
+import backoff
 from googleapiclient.discovery import build
 from googleapiclient.errors import HttpError
 from google.oauth2 import service_account
@@ -60,6 +61,7 @@ async def get_google_service():
         logger.error(f"Failed to initialize Google service: {e}")
         raise
 
+@backoff.on_exception(backoff.expo, HttpError, max_tries=5, base=5, giveup=lambda e: e.resp.status not in [429, 500, 502, 503, 504])
 async def ensure_google_calendar(service, employee_kuerzel):
     """Ensure Google Calendar exists for employee."""
     calendar_name = f"AW-{employee_kuerzel}"
@@ -106,6 +108,7 @@ async def fetch_advoware_appointments(advoware, employee_kuerzel):
         logger.error(f"Failed to fetch Advoware appointments: {e}")
         raise
 
+@backoff.on_exception(backoff.expo, HttpError, max_tries=5, base=5, giveup=lambda e: e.resp.status not in [429, 500, 502, 503, 504])
 async def fetch_google_events(service, calendar_id):
     """Fetch Google events in range."""
     try:
@@ -287,6 +290,7 @@ async def delete_advoware_appointment(advoware, frnr):
         logger.error(f"Failed to delete Advoware appointment {frnr}: {e}")
         raise
 
+@backoff.on_exception(backoff.expo, HttpError, max_tries=5, base=5, giveup=lambda e: e.resp.status not in [429, 500, 502, 503, 504])
 async def create_google_event(service, calendar_id, data):
     """Create Google event from standardized data."""
     start_dt = data['start'].astimezone(BERLIN_TZ)
@@ -320,6 +324,7 @@ async def create_google_event(service, calendar_id, data):
         logger.error(f"Failed to create Google event: {e}")
         raise
 
+@backoff.on_exception(backoff.expo, HttpError, max_tries=5, base=5, giveup=lambda e: e.resp.status not in [429, 500, 502, 503, 504])
 async def update_google_event(service, calendar_id, event_id, data):
     """Update Google event."""
     start_dt = data['start'].astimezone(BERLIN_TZ)
@@ -351,6 +356,7 @@ async def update_google_event(service, calendar_id, event_id, data):
         logger.error(f"Failed to update Google event {event_id}: {e}")
         raise
 
+@backoff.on_exception(backoff.expo, HttpError, max_tries=5, base=5, giveup=lambda e: e.resp.status not in [429, 500, 502, 503, 504])
 async def delete_google_event(service, calendar_id, event_id):
     """Delete Google event."""
     try: