test: fix today_test flakiness with London-timezone-aware booking times

Replace clock.Now() with fixed London-timezone times in TestGetCurrentNext_WithMultipleDataPoints to prevent near-midnight UTC failures where bookings fall outside the London 'today' window.

backend/handlers/today/today_test.go

@@ -680,7 +680,14 @@ func TestGetCurrentNext_WithData(t *testing.T) {
 func TestGetCurrentNext_WithMultipleDataPoints(t *testing.T) {
 	ctx, tx := testutils.SetupTestTx(t)
 
-	now := clock.Now()
+	londonNow := clock.Now().In(clock.London)
+	// Use fixed times within today's London business hours so the handler's
+	// London-midnight date range always includes both bookings regardless of
+	// when the test runs (runs near midnight UTC could push one booking
+	// outside the London "today" window).
+	todayAt := func(h, m int) time.Time {
+		return time.Date(londonNow.Year(), londonNow.Month(), londonNow.Day(), h, m, 0, 0, clock.London).UTC()
+	}
 	svcID := createTodayService(t, ctx, tx)
 
 	user1ID, err := fixtures.CreateTestUser(tx)
@@ -693,7 +700,7 @@ func TestGetCurrentNext_WithMultipleDataPoints(t *testing.T) {
 		INSERT INTO bookings (user_id, start_time, status)
 		VALUES ($1, $2, 'completed')
 		RETURNING id
-	`, user1ID, now.Add(-30*time.Minute)).Scan(&booking1ID)
+	`, user1ID, todayAt(10, 0)).Scan(&booking1ID)
 	if err != nil {
 		t.Fatalf("failed to create booking 1: %v", err)
 	}
@@ -725,7 +732,7 @@ func TestGetCurrentNext_WithMultipleDataPoints(t *testing.T) {
 		INSERT INTO bookings (user_id, start_time, status)
 		VALUES ($1, $2, 'completed')
 		RETURNING id
-	`, user2ID, now.Add(-15*time.Minute)).Scan(&booking2ID)
+	`, user2ID, todayAt(11, 0)).Scan(&booking2ID)
 	if err != nil {
 		t.Fatalf("failed to create booking 2: %v", err)
 	}