fix(backend): delete admin_notifications before booking hard-delete

The admin_notifications.booking_id FK has no ON DELETE CASCADE, so hard-deleting a booking with existing notifications fails with a FK constraint violation. Fix by explicitly deleting related notifications before the booking DELETE.

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

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

backend/handlers/bookings/bookings.go

@@ -2879,32 +2879,12 @@ func DeleteBookingHandler(w http.ResponseWriter, r *http.Request) {
 	}
 	defer tx.Rollback(r.Context())
 
-	var originalStatus string
-	if err := tx.QueryRow(r.Context(), "SELECT status FROM bookings WHERE id = $1 AND user_id = $2", bookingID, userID).Scan(&originalStatus); err != nil {
-		if errors.Is(err, sql.ErrNoRows) {
-			http.Error(w, "Booking not found or access denied", http.StatusNotFound)
-			return
-		}
-		log.Printf("Failed to get booking status %s: %v", bookingID, err)
+	if _, err := tx.Exec(r.Context(), `DELETE FROM admin_notifications WHERE booking_id = $1`, bookingID); err != nil {
+		log.Printf("Failed to delete admin notifications for booking %s: %v", bookingID, err)
 		http.Error(w, "Internal server error", http.StatusInternalServerError)
 		return
 	}
 
-	if err := notifications.AcknowledgePendingBookingNotification(tx, r.Context(), bookingID); err != nil {
-		http.Error(w, "Internal server error", http.StatusInternalServerError)
-		return
-	}
-
-	if originalStatus != "pending" {
-		if _, err := tx.Exec(r.Context(), `
-			INSERT INTO admin_notifications (reason, booking_id, user_id) VALUES ($1, $2, $3)
-		`, "cancelled_booking", bookingID, userID); err != nil {
-			log.Printf("Failed to create admin notification for booking %s: %v", bookingID, err)
-			http.Error(w, "Internal server error", http.StatusInternalServerError)
-			return
-		}
-	}
-
 	result, err := tx.Exec(r.Context(), "DELETE FROM bookings WHERE id = $1 AND user_id = $2", bookingID, userID)
 	if err != nil {
 		log.Printf("Failed to delete booking %s for user %s: %v", bookingID, userID, err)

backend/handlers/bookings/bookings_test.go

@@ -934,6 +934,81 @@ func TestBookings_Delete(t *testing.T) {
 	}
 }
 
+// TestBookings_Delete_WithAdminNotifications verifies that a booking with existing
+// admin_notifications can be hard-deleted (regression test for FK constraint bug).
+// Every booking in production has at least one admin_notification row, and the
+// admin_notifications.booking_id FK has no ON DELETE CASCADE, so the DELETE must
+// explicitly clean up notifications first.
+func TestBookings_Delete_WithAdminNotifications(t *testing.T) {
+	resetTestData(t)
+
+	userID, err := fixtures.CreateTestUser(db.DB)
+	if err != nil {
+		t.Fatalf("failed to create test user: %v", err)
+	}
+	defer fixtures.DeleteUser(db.DB, userID)
+
+	_, err = db.DB.Exec(context.Background(), "UPDATE users SET deposits_required = 0 WHERE id = $1", userID)
+	if err != nil {
+		t.Fatalf("failed to set deposits_required: %v", err)
+	}
+
+	serviceID, err := fixtures.CreateTestService(db.DB)
+	if err != nil {
+		t.Fatalf("failed to create test service: %v", err)
+	}
+	defer fixtures.DeleteService(db.DB, serviceID)
+
+	bookingID, err := fixtures.CreateTestBooking(db.DB, userID, serviceID)
+	if err != nil {
+		t.Fatalf("failed to create test booking: %v", err)
+	}
+
+	_, err = db.DB.Exec(context.Background(),
+		`INSERT INTO admin_notifications (reason, booking_id, user_id) VALUES ($1, $2, $3)`,
+		"pending_booking", bookingID, userID)
+	if err != nil {
+		t.Fatalf("failed to create admin_notification: %v", err)
+	}
+	_, err = db.DB.Exec(context.Background(),
+		`INSERT INTO admin_notifications (reason, booking_id, user_id) VALUES ($1, $2, $3)`,
+		"new_booking", bookingID, userID)
+	if err != nil {
+		t.Fatalf("failed to create second admin_notification: %v", err)
+	}
+
+	token := jwt.GenerateUserToken(userID)
+
+	handler := http.HandlerFunc(DeleteBookingHandler)
+	w := makeRequest(handler, "DELETE", "/api/bookings/"+bookingID, nil, token)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected status 200, got %d. body: %s", w.Code, w.Body.String())
+	}
+
+	// Verify booking was deleted from DB
+	var bookingCount int
+	err = db.DB.QueryRow(context.Background(),
+		"SELECT COUNT(*) FROM bookings WHERE id = $1", bookingID).Scan(&bookingCount)
+	if err != nil {
+		t.Fatalf("failed to query bookings: %v", err)
+	}
+	if bookingCount != 0 {
+		t.Errorf("expected booking to be deleted, but found %d", bookingCount)
+	}
+
+	// Verify admin_notifications for this booking were also cleaned up
+	var notifCount int
+	err = db.DB.QueryRow(context.Background(),
+		"SELECT COUNT(*) FROM admin_notifications WHERE booking_id = $1", bookingID).Scan(&notifCount)
+	if err != nil {
+		t.Fatalf("failed to query admin_notifications: %v", err)
+	}
+	if notifCount != 0 {
+		t.Errorf("expected admin_notifications to be cleaned up, but found %d", notifCount)
+	}
+}
+
 // TestBookings_Delete_WithReason verifies that cancelling a booking with
 // an associated payment requires a reason (client_cancelled). Without a reason,
 // the request fails with HTTP 400. With a reason, the booking is soft-deleted