feat: enhance driver absence backend with leave support and request-type filtering

Persist leave-specific fields in DriverAbsence by saving leaveType and otherLeaveDescription during create/update flows (including UUID update path), and clear leave fields when request type is ABSENCE. Extend DriverAbsence mapper to map leaveType and otherLeaveDescription both ways for consistent storage and API responses. Add requestType filtering to processed/unprocessed driver absence list endpoints by propagating requestType through controller, service interface/implementation, parser, and JPA specifications. Enrich planning absences endpoint (/api/absence/driver/drivers?date=...) response with requestType, leaveType, and otherLeaveDescription, and update reason mapping logic with null-safe handling to avoid NPEs.