fix: handle invalid date and time values in draft/record APIs

- Add clean_date_value() helper function to convert empty/invalid dates
  ('0000-00-00', empty string) to NULL before database operations
- Apply date cleaning to form_date, date_of_birth, ob_lmp, and ob_edc
  fields in autosave_draft.php
- Add cleanup logic in get_draft.php and get_record.php to prevent loading
  '00:00:00' and '0000-00-00' values into forms (converts to empty strings)
- Fix field name inconsistency: change 'delivery_time' to 'ob_delivery_time'
  in get_record.php for consistency with database schema
- Update Claude settings with Git Bash style path permission

This prevents invalid database values from being displayed in forms and
ensures proper NULL handling for empty date/time fields, improving data
quality and preventing validation errors in the UI.
