feat: edit request time blockers, today closing time, UI polish, and test fixes

- Add time blocker management for booking edit requests
- Add closing_time field to admin today/current-next endpoint
- Update UserBookingModal and CurrentAppointment UI components
- Fix fmt import in bookings_test.go (was missing)
- Fix created_by FK in TestAdminApproveEditRequest_TimeBlockerOverlap
- Update test coverage for edit request time blocker overlap
- Update gap backlog documentation

backend/handlers/scheduling/time-blockers.go

@@ -343,6 +343,7 @@ func CleanupOldReservations(ctx context.Context) error {
 	oneHourAgo := time.Now().Add(-1 * time.Hour)
 	tenMinutesAgo := time.Now().Add(-10 * time.Minute)
 	fifteenMinutesAgo := time.Now().Add(-15 * time.Minute)
+	twentyFourHoursAgo := time.Now().Add(-24 * time.Hour)
 
 	_, err := db.DB.Exec(ctx, `
 		DELETE FROM time_blockers
@@ -350,7 +351,8 @@ func CleanupOldReservations(ctx context.Context) error {
 		   OR (description LIKE 'RESERVATION:anon:%' AND created_at < $2)
 		   OR (description LIKE 'RESERVATION:admin:walkin:%' AND created_at < $3)
 		   OR (description LIKE 'RESERVATION:admin:callin:%' AND created_at < $3)
-	`, oneHourAgo, tenMinutesAgo, fifteenMinutesAgo)
+		   OR (description LIKE 'RESERVATION:edit_request:%' AND created_at < $4)
+	`, oneHourAgo, tenMinutesAgo, fifteenMinutesAgo, twentyFourHoursAgo)
 	return err
 }