Fix monthly actuals: allow negative values and fix save/reconcile error

- Remove min={0} from NumberInput to allow negative actuals (refunds/corrections)
- Fix post() in journal-entries service: use id param directly instead of
  RETURNING result which returns [rows, count] in TypeORM QueryRunner
- Handle negative amounts in saveActuals(): negative expense credits the
  expense account, negative income debits the income account

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/modules/monthly-actuals/monthly-actuals.service.ts

@@ -127,25 +127,28 @@ export class MonthlyActualsService {
     for (const line of filteredLines) {
       const acctType = accountTypeMap.get(line.accountId);
       if (!acctType) continue;
+      const abs = Math.abs(line.amount);
 
       if (acctType === 'expense') {
-        // Expense: debit expense account, credit cash
-        jeLines.push({
-          accountId: line.accountId,
-          debit: Math.abs(line.amount),
-          credit: 0,
-          memo: `${monthLabel} actual`,
-        });
-        totalCashCredit += Math.abs(line.amount);
+        if (line.amount > 0) {
+          // Normal expense: debit expense, credit cash
+          jeLines.push({ accountId: line.accountId, debit: abs, credit: 0, memo: `${monthLabel} actual` });
+          totalCashCredit += abs;
+        } else {
+          // Negative expense (refund/correction): credit expense, debit cash
+          jeLines.push({ accountId: line.accountId, debit: 0, credit: abs, memo: `${monthLabel} actual (correction)` });
+          totalCashDebit += abs;
+        }
       } else if (acctType === 'income') {
-        // Income: credit income account, debit cash
-        jeLines.push({
-          accountId: line.accountId,
-          debit: 0,
-          credit: Math.abs(line.amount),
-          memo: `${monthLabel} actual`,
-        });
-        totalCashDebit += Math.abs(line.amount);
+        if (line.amount > 0) {
+          // Normal income: credit income, debit cash
+          jeLines.push({ accountId: line.accountId, debit: 0, credit: abs, memo: `${monthLabel} actual` });
+          totalCashDebit += abs;
+        } else {
+          // Negative income (correction): debit income, credit cash
+          jeLines.push({ accountId: line.accountId, debit: abs, credit: 0, memo: `${monthLabel} actual (correction)` });
+          totalCashCredit += abs;
+        }
       }
     }