feat: #44 fatura de cartão com data futura fica pendente até confirmação

- Nova tabela pending_bill_imports (migration 016)
- ImportHandler.Confirm: quando is_credit_card=true e payment_date > hoje,
  salva como pending em vez de inserir transações
- Novos endpoints: GET /pending-bills, POST /pending-bills/:id/confirm,
  DELETE /pending-bills/:id
- Dashboard inclui pending_bill_imports no payload
- Frontend: resultado "fatura salva como pendente" no ImportView
- AccountsView exibe widget de faturas pendentes com ações de confirmar/descartar
- dashboard_test: mock de PendingBillRepo + TransactionRepository

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

apps/api/internal/migration/migration.go

@@ -53,6 +53,9 @@ var m014 string
 //go:embed sql/015_accounts_cdi_percentage.sql
 var m015 string
 
+//go:embed sql/016_pending_bill_imports.sql
+var m016 string
+
 func Run(ctx context.Context, pool *pgxpool.Pool) error {
 	// Bootstrap: ensure schema_migrations table exists before checking versions.
 	if _, err := pool.Exec(ctx, `
@@ -64,7 +67,7 @@ func Run(ctx context.Context, pool *pgxpool.Pool) error {
 		return fmt.Errorf("bootstrap schema_migrations: %w", err)
 	}
 
-	migrations := []string{m001, m002, m003, m004, m005, m006, m007, m008, m009, m010, m011, m012, m013, m014, m015}
+	migrations := []string{m001, m002, m003, m004, m005, m006, m007, m008, m009, m010, m011, m012, m013, m014, m015, m016}
 	for i, sql := range migrations {
 		version := i + 1
 		var applied bool