Enhance EspoCRM API and Webhook Handling

- Improved logging for file uploads in EspoCRMAPI to include upload parameters and error details.
- Updated cron job configurations for calendar sync and participant sync to trigger every 15 minutes on the first minute of the hour.
- Enhanced document create, delete, and update webhook handlers to determine and log the entity type.
- Refactored document sync event handler to include entity type in sync operations and logging.
- Added a new test script for uploading preview images to EspoCRM and verifying the upload process.
- Created a test script for document thumbnail generation, including document creation, file upload, webhook triggering, and preview verification.

steps/vmh/beteiligte_sync_cron_step.py

@@ -19,7 +19,7 @@ config = {
     "description": "Prüft alle 15 Minuten welche Beteiligte synchronisiert werden müssen",
     "flows": ["vmh-beteiligte"],
     "triggers": [
-        cron("0 */15 * * * *")  # Alle 15 Minuten (6-field format!)
+        cron("0 */15 1 * * *")  # Alle 15 Minuten (6-field format!)
     ],
     "enqueues": ["vmh.beteiligte.sync_check"]
 }