feat(loyalty-discount): implement loyalty and discount system

- Add discount campaign management and validation logic
- Update booking handlers with discount application flow
- Add customer relationship endpoints for loyalty tracking
- Update frontend modals (booking, approval, payment, reschedule)
- Add DiscountsManagement and loyalty reference documentation
- Update dev scripts and database init for discount tables
- Clean up completed plan files

backend/handlers/user/customer_relationship.go

@@ -18,6 +18,7 @@ import (
 
 type CustomerRelationship struct {
 	TotalSpend     float64      `json:"totalSpend"`
+	TotalSaved     float64      `json:"totalSaved"`
 	TotalTips      float64      `json:"totalTips"`
 	TotalVisits    int          `json:"totalVisits"`
 	CustomerFor    string       `json:"customerFor"`
@@ -62,11 +63,25 @@ func GetCustomerRelationshipHandler(w http.ResponseWriter, r *http.Request) {
 		WHERE b.user_id = $1
 		  AND p.status = 'completed'
 		  AND p.payment_type IN ('full', 'partial', 'balance', 'deposit')
+		  AND p.payment_method != 'discount'
 	`, userID).Scan(&result.TotalSpend)
 	if err != nil && !errors.Is(err, sql.ErrNoRows) {
 		log.Printf("Failed to get total spend for user %s: %v", userID, err)
 	}
 
+	err = db.DB.QueryRow(r.Context(), `
+		SELECT COALESCE(SUM(p.amount), 0)
+		FROM payments p
+		JOIN bookings b ON p.booking_id = b.id
+		WHERE b.user_id = $1
+		  AND p.status = 'completed'
+		  AND p.payment_type IN ('full', 'partial', 'balance', 'deposit')
+		  AND p.payment_method = 'discount'
+	`, userID).Scan(&result.TotalSaved)
+	if err != nil && !errors.Is(err, sql.ErrNoRows) {
+		log.Printf("Failed to get total saved for user %s: %v", userID, err)
+	}
+
 	err = db.DB.QueryRow(r.Context(), `
 		SELECT COALESCE(SUM(p.amount), 0)
 		FROM payments p

backend/handlers/user/customer_relationship_test.go

@@ -318,3 +318,56 @@ func createPayment(t *testing.T, pool *pgxpool.Pool, bookingID, paymentType stri
 		t.Fatalf("failed to create payment: %v", err)
 	}
 }
+
+func TestCustomerRelationship_WithDiscounts(t *testing.T) {
+	resetTestData(t)
+
+	userID, err := fixtures.CreateTestUser(db.DB)
+	if err != nil {
+		t.Fatalf("failed to create test user: %v", err)
+	}
+
+	svcID, err := createService(db.DB, "Test Service", 100.00)
+	if err != nil {
+		t.Fatalf("failed to create service: %v", err)
+	}
+
+	bookingID := createCompletedBooking(t, db.DB, userID, svcID, "2024-03-01 10:00:00+00", 100.00)
+
+	// User pays £80.00 cash/card and receives £20.00 discount
+	createPayment(t, db.DB, bookingID, "balance", 80.00)
+	createDiscountPayment(t, db.DB, bookingID, 20.00)
+
+	req := newAdminRequest("GET", "/api/admin/users/"+userID+"/relationship", userID)
+	rr := httptest.NewRecorder()
+	GetCustomerRelationshipHandler(rr, req)
+
+	if rr.Code != http.StatusOK {
+		t.Fatalf("expected status 200, got %d. body: %s", rr.Code, rr.Body.String())
+	}
+
+	var result CustomerRelationship
+	if err := json.Unmarshal(rr.Body.Bytes(), &result); err != nil {
+		t.Fatalf("failed to unmarshal response: %v", err)
+	}
+
+	if result.TotalSpend != 80.00 {
+		t.Errorf("expected total spend 80.00, got %.2f", result.TotalSpend)
+	}
+
+	if result.TotalSaved != 20.00 {
+		t.Errorf("expected total saved 20.00, got %.2f", result.TotalSaved)
+	}
+}
+
+func createDiscountPayment(t *testing.T, pool *pgxpool.Pool, bookingID string, amount float64) {
+	t.Helper()
+	ctx := context.Background()
+	_, err := pool.Exec(ctx, `
+		INSERT INTO payments (booking_id, payment_type, payment_method, amount, status)
+		VALUES ($1, 'partial', 'discount', $2, 'completed')
+	`, bookingID, amount)
+	if err != nil {
+		t.Fatalf("failed to create discount payment: %v", err)
+	}
+}