feat(#19): registro manual de transações e recorrências fixas

Adiciona CRUD manual de transações (income/expense) com filtro mensal, CRUD de
recorrências fixas com verificação mensal de cobertura (±10% por categoria),
endpoint de ignore/unignore e telas Vue para Transações e Configurações.

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

apps/api/internal/service/transaction.go

@@ -0,0 +1,74 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"strings"
+
+	"financeiro-carvalho/internal/model"
+	"financeiro-carvalho/internal/repository"
+)
+
+var (
+	ErrInvalidTransactionType   = errors.New("type must be 'income' or 'expense'")
+	ErrCannotEditImported       = errors.New("imported transactions cannot be edited or deleted")
+	ErrTransactionEmptyDesc     = errors.New("description is required")
+	ErrTransactionInvalidAmount = errors.New("amount must be greater than zero")
+)
+
+type TransactionService struct {
+	repo repository.ManualTransactionRepository
+}
+
+func NewTransactionService(repo repository.ManualTransactionRepository) *TransactionService {
+	return &TransactionService{repo: repo}
+}
+
+func (s *TransactionService) List(ctx context.Context, month string) ([]model.Transaction, error) {
+	txs, err := s.repo.List(ctx, month)
+	if txs == nil {
+		return []model.Transaction{}, err
+	}
+	return txs, err
+}
+
+func (s *TransactionService) Create(ctx context.Context, t model.Transaction) (*model.Transaction, error) {
+	if err := validateTransaction(t); err != nil {
+		return nil, err
+	}
+	t.Description = strings.TrimSpace(t.Description)
+	return s.repo.Create(ctx, t)
+}
+
+func (s *TransactionService) Update(ctx context.Context, t model.Transaction) (*model.Transaction, error) {
+	if err := validateTransaction(t); err != nil {
+		return nil, err
+	}
+	t.Description = strings.TrimSpace(t.Description)
+	out, err := s.repo.Update(ctx, t)
+	if errors.Is(err, repository.ErrNotFound) {
+		return nil, ErrCannotEditImported
+	}
+	return out, err
+}
+
+func (s *TransactionService) Delete(ctx context.Context, id int) error {
+	err := s.repo.Delete(ctx, id)
+	if errors.Is(err, repository.ErrNotFound) {
+		return ErrCannotEditImported
+	}
+	return err
+}
+
+func validateTransaction(t model.Transaction) error {
+	if strings.TrimSpace(t.Description) == "" {
+		return ErrTransactionEmptyDesc
+	}
+	if t.Amount <= 0 {
+		return ErrTransactionInvalidAmount
+	}
+	if t.Type != "income" && t.Type != "expense" {
+		return ErrInvalidTransactionType
+	}
+	return nil
+}