feat(#20): dashboard financeiro mensal — 4 widgets + endpoint de agregação

Adiciona GET /api/dashboard?month=YYYY-MM com resumo mensal (% poupado,
gastos por categoria, evolução 6 meses, últimas 10 transações, recorrências
pendentes). HomeView.vue reescrita com 4 widgets e gráficos CSS nativos.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

apps/api/internal/service/dashboard_test.go

@@ -0,0 +1,82 @@
+package service_test
+
+import (
+	"context"
+	"testing"
+
+	"financeiro-carvalho/internal/model"
+	"financeiro-carvalho/internal/service"
+)
+
+type mockDashboardRepo struct {
+	income   float64
+	expenses float64
+}
+
+func (m *mockDashboardRepo) MonthlySummary(_ context.Context, _ string) (float64, float64, error) {
+	return m.income, m.expenses, nil
+}
+func (m *mockDashboardRepo) ByCategory(_ context.Context, _ string) ([]model.CategoryTotal, error) {
+	return nil, nil
+}
+func (m *mockDashboardRepo) MonthlyEvolution(_ context.Context, _ string) ([]model.MonthEvolution, error) {
+	return nil, nil
+}
+func (m *mockDashboardRepo) RecentTransactions(_ context.Context, _ string) ([]model.RecentTransaction, error) {
+	return nil, nil
+}
+
+func newDashboardSvc(income, expenses float64) *service.DashboardService {
+	recurrSvc := service.NewRecurringService(newMockRecurring(nil), &mockTxRepo{})
+	return service.NewDashboardService(&mockDashboardRepo{income: income, expenses: expenses}, recurrSvc)
+}
+
+func TestDashboard_SavingsPct_40(t *testing.T) {
+	svc := newDashboardSvc(10000, 6000)
+	data, err := svc.Get(context.Background(), "2024-03")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if data.SavingsPct != 40.0 {
+		t.Errorf("expected 40.0, got %.2f", data.SavingsPct)
+	}
+}
+
+func TestDashboard_SavingsPct_NoIncome(t *testing.T) {
+	svc := newDashboardSvc(0, 500)
+	data, err := svc.Get(context.Background(), "2024-03")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if data.SavingsPct != 0 {
+		t.Errorf("expected 0.0 when no income, got %.2f", data.SavingsPct)
+	}
+}
+
+func TestDashboard_SavingsPct_Above40(t *testing.T) {
+	svc := newDashboardSvc(10000, 5000)
+	data, err := svc.Get(context.Background(), "2024-03")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if data.SavingsPct != 50.0 {
+		t.Errorf("expected 50.0, got %.2f", data.SavingsPct)
+	}
+}
+
+func TestDashboard_EmptySlices(t *testing.T) {
+	svc := newDashboardSvc(0, 0)
+	data, err := svc.Get(context.Background(), "2024-03")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if data.ByCategory == nil {
+		t.Error("ByCategory should not be nil")
+	}
+	if data.MonthlyEvolution == nil {
+		t.Error("MonthlyEvolution should not be nil")
+	}
+	if data.RecentTransactions == nil {
+		t.Error("RecentTransactions should not be nil")
+	}
+}