test: fix flaky time_blockers test and improve testdb migration

Un-harden TestTimeBlockers_List dates (now relative to current time) and
update TestCleanupOldReservations to use fixture users instead of hardcoded IDs.
Improve Migrate() to drop types before tables (CASCADE dependency fix) and
add forgiven_no_shows to truncate list. Seed default working hours in admin
booking tests to prevent business-logic check failures.

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

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

backend/handlers/admin/bookings_test.go

@@ -39,6 +39,39 @@ import (
 )
 
 // =============================================================================
+func seedDefaultWorkingHours(t *testing.T) {
+	t.Helper()
+
+	// Seed 7 days of working hours (Monday=0 to Sunday=6)
+	// Use wide hours to avoid test failures due to business logic time checks
+	hours := []struct {
+		weekday   int
+		startTime string
+		endTime   string
+		isOpen    bool
+	}{
+		{0, "08:00", "20:00", true}, // Monday
+		{1, "08:00", "20:00", true}, // Tuesday
+		{2, "08:00", "20:00", true}, // Wednesday
+		{3, "08:00", "20:00", true}, // Thursday
+		{4, "08:00", "20:00", true}, // Friday
+		{5, "08:00", "20:00", true}, // Saturday
+		{6, "08:00", "20:00", true}, // Sunday
+	}
+
+	for _, h := range hours {
+		_, err := db.DB.Exec(context.Background(), `
+			INSERT INTO working_hours (weekday, start_time, end_time, is_open)
+			VALUES ($1, $2, $3, $4)
+			ON CONFLICT (weekday) DO UPDATE SET start_time = $2, end_time = $3, is_open = $4
+		`, h.weekday, h.startTime, h.endTime, h.isOpen)
+		if err != nil {
+			t.Fatalf("failed to seed working hours: %v", err)
+		}
+	}
+}
+
+
 // List Admin Bookings Tests
 // =============================================================================