feat: scheduling exceptional hours support and default hours validation

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/main.go

@@ -259,6 +259,10 @@ func main() {
 				r.Get("/{id}", bookings.GetAdminBookingHandler)
 				r.Put("/{id}", bookings.UpdateBookingServicesHandler)
 				r.Get("/{id}/overlapping", bookings.GetOverlappingBookingsHandler)
+				r.Get("/overlapping", bookings.GetOverlappingBookingsByTimeHandler)
+				r.Get("/by-date-range", bookings.GetBookingsByDateRangeHandler)
+				r.Get("/by-created-range", bookings.GetBookingsByCreatedRangeHandler)
+				r.Put("/{id}/reschedule", bookings.AdminRescheduleBookingHandler)
 				r.Put("/{id}/progress", bookings.ProgressBookingHandler)
 				r.Post("/{id}/confirm", bookings.ConfirmBookingHandler)
 				r.Post("/{id}/cancel", bookings.AdminCancelBookingHandler)