ab4b9fe6fc
- Recurrence conflict checking: check ALL occurrences in recurrence loop - Cascade update transaction safety: add conflict checking for shifted appointments - Client deletion integrity: check for existing appointments before delete - Email notification error handling: add retry wrapper (max 2 retries, 1s delay) - Null guards on recurrence result: validate inserted after each insert Co-Authored-By: Paperclip <noreply@paperclip.ing>