feat: categoria is_tax exclui impostos do denominador do savings_pct

savings_pct = (receita - despesas) / (receita - impostos).
Toggle IMPOSTO no CRUD de categorias; badge dourado na lista.

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

apps/api/internal/service/category.go

@@ -32,14 +32,14 @@ func (s *CategoryService) Create(ctx context.Context, in model.CategoryInput) (*
 	if err := validateInput(in); err != nil {
 		return nil, err
 	}
-	return s.repo.Create(ctx, strings.TrimSpace(in.Name), in.Color)
+	return s.repo.Create(ctx, strings.TrimSpace(in.Name), in.Color, in.IsTax)
 }
 
 func (s *CategoryService) Update(ctx context.Context, id int, in model.CategoryInput) (*model.Category, error) {
 	if err := validateInput(in); err != nil {
 		return nil, err
 	}
-	return s.repo.Update(ctx, id, strings.TrimSpace(in.Name), in.Color)
+	return s.repo.Update(ctx, id, strings.TrimSpace(in.Name), in.Color, in.IsTax)
 }
 
 func (s *CategoryService) Delete(ctx context.Context, id int) error {

apps/api/internal/service/dashboard.go

@@ -8,6 +8,7 @@ import (
 
 type DashboardRepo interface {
 	MonthlySummary(ctx context.Context, month string) (income, expenses float64, err error)
+	TotalTaxes(ctx context.Context, month string) (float64, error)
 	ByCategory(ctx context.Context, month string) ([]model.CategoryTotal, error)
 	MonthlyEvolution(ctx context.Context, month string) ([]model.MonthEvolution, error)
 	RecentTransactions(ctx context.Context, month string) ([]model.RecentTransaction, error)
@@ -34,6 +35,11 @@ func (s *DashboardService) Get(ctx context.Context, month string) (*model.Dashbo
 		return nil, err
 	}
 
+	taxes, err := s.repo.TotalTaxes(ctx, month)
+	if err != nil {
+		return nil, err
+	}
+
 	byCategory, err := s.repo.ByCategory(ctx, month)
 	if err != nil {
 		return nil, err
@@ -49,9 +55,11 @@ func (s *DashboardService) Get(ctx context.Context, month string) (*model.Dashbo
 		return nil, err
 	}
 
+	// savings_pct uses net income (gross - taxes) as denominator (Option B)
 	var savingsPct float64
-	if income > 0 {
-		savingsPct = (income - expenses) / income * 100
+	netIncome := income - taxes
+	if netIncome > 0 {
+		savingsPct = (income - expenses) / netIncome * 100
 	}
 
 	statuses, err := s.recurrSvc.MonthlyStatus(ctx, month)

apps/api/internal/service/dashboard_test.go

@@ -16,6 +16,9 @@ type mockDashboardRepo struct {
 func (m *mockDashboardRepo) MonthlySummary(_ context.Context, _ string) (float64, float64, error) {
 	return m.income, m.expenses, nil
 }
+func (m *mockDashboardRepo) TotalTaxes(_ context.Context, _ string) (float64, error) {
+	return 0, nil
+}
 func (m *mockDashboardRepo) ByCategory(_ context.Context, _ string) ([]model.CategoryTotal, error) {
 	return nil, nil
 }