feat: add finance module with yearly income/expense tracking

- FinanceEntry model (income/expense x fixed/extra)
- CRUD API endpoints for finance entries
- FinancePage with summary cards and drill-down
- Updated navigation with Finance tab
- Updated todos default filter to active

internal/service/service.go

@@ -97,3 +97,27 @@ func (s *DailyLogService) Save(date, morning, afternoon, evening string) (*model
 	err := s.repo.Upsert(log)
 	return log, err
 }
+
+type FinanceService struct {
+	repo *repository.FinanceRepository
+}
+
+func NewFinanceService(repo *repository.FinanceRepository) *FinanceService {
+	return &FinanceService{repo: repo}
+}
+
+func (s *FinanceService) GetByYear(year int) ([]model.FinanceEntry, error) {
+	return s.repo.GetByYear(year)
+}
+
+func (s *FinanceService) Create(entry *model.FinanceEntry) error {
+	return s.repo.Create(entry)
+}
+
+func (s *FinanceService) Update(entry *model.FinanceEntry) error {
+	return s.repo.Update(entry)
+}
+
+func (s *FinanceService) Delete(id uint64) error {
+	return s.repo.Delete(id)
+}