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/admin/today_test.go

@@ -19,6 +19,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"testing"
+	"time"
 
 	"crussell/db"
 	"crussell/handlers/notifications"
@@ -102,6 +103,51 @@ func TestAdminToday_CurrentNext(t *testing.T) {
 	}
 }
 
+// TestAdminToday_CurrentNext_ClosingTime verifies that the current-next endpoint
+// returns the closing time for today.
+func TestAdminToday_CurrentNext_ClosingTime(t *testing.T) {
+	cleanup := setupTestDB(t)
+	defer cleanup()
+
+	// Seed working hours for today (query uses current weekday)
+	todayWeekday := int(time.Now().Weekday())
+	if todayWeekday == 0 {
+		todayWeekday = 7
+	}
+	_, err := db.DB.Exec(context.Background(), `
+		INSERT INTO working_hours (weekday, start_time, end_time, is_open)
+		VALUES ($1, '09:00', '18:00', true)
+		ON CONFLICT (weekday) DO UPDATE SET start_time = '09:00', end_time = '18:00', is_open = true
+	`, todayWeekday)
+	if err != nil {
+		t.Fatalf("failed to seed working hours: %v", err)
+	}
+
+	handler := http.HandlerFunc(today.GetCurrentAndNextHandler)
+	w := makeAdminRequest(handler, "GET", "/api/admin/today/current-next", nil)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected status 200, got %d. body: %s", w.Code, w.Body.String())
+	}
+
+	var response today.CurrentNextResponse
+	if err := json.Unmarshal(w.Body.Bytes(), &response); err != nil {
+		t.Fatalf("failed to unmarshal response: %v", err)
+	}
+
+	if response.ClosingTime == nil {
+		t.Errorf("expected closing_time in response, got nil")
+	}
+
+	if response.ClosingTime != nil && *response.ClosingTime == "" {
+		t.Error("expected closing_time to be non-empty string")
+	}
+
+	if response.ClosingTime != nil && *response.ClosingTime != "18:00:00" && *response.ClosingTime != "18:00" {
+		t.Logf("got closing_time: %s", *response.ClosingTime)
+	}
+}
+
 // TestAdminToday_Appointments tests that an admin can get a list of all
 // bookings scheduled for today with their details.
 func TestAdminToday_Appointments(t *testing.T) {