fix(expenses): guard aggregate amount ranges

docs/reference/api.md

@@ -377,8 +377,12 @@ Router: `main/routes/expenses.ts`. Full path: `/api/expenses`. Reads need `expen
 creation, voiding, and replacement need `expenses.manage` **and** `expenses.view`, while payment and
 reversal mutations need `expenses.pay` and `expenses.reverse` (alongside `expenses.view`, plus
 `cash.movements.manage` for cash methods) so an actor can always read back the row they touched.
-Amounts are integer minor units in the expense's own `currency_code`; no endpoint converts currencies
-or assumes a minor-unit factor.
+Amounts are positive safe-integer minor units in the expense's own `currency_code`; no endpoint
+converts currencies or assumes a minor-unit factor. Active incurred totals per currency (after
+subtracting the replaced source on replacement) and returned aggregate totals must fit within
+`Number.MAX_SAFE_INTEGER`, or the operation fails with `422 amount_range_exceeded`; legacy rows with
+an out-of-range stored amount project `amount_minor` and `due_minor` as `null` so list, detail, and
+recovery mutations stay usable without rounding.
 
 | Method | Path | Authorization | Parameters | Response |
 | --- | --- | --- | --- | --- |

frontend/src/components/expenses/ExpenseWorkflow.tsx

@@ -144,8 +144,12 @@ export default function ExpenseWorkflow({
     setAttemptState({ attempt: next, storageBlocked: false });
   // The freshly loaded record wins over the list row once it is that same record.
   const record = detail && detail.id === expense?.id ? detail : expense;
-  const fmtMinor = (amountMinor: number) =>
-    fmt(amountMinor / getCurrencyMinorUnitFactor(record?.currency_code ?? context.currency_code));
+  const fmtMinor = (amountMinor: number | null) =>
+    amountMinor === null
+      ? tCommon('notAvailable')
+      : fmt(
+          amountMinor / getCurrencyMinorUnitFactor(record?.currency_code ?? context.currency_code),
+        );
 
   /** Replacing copies the source values into the fresh form. */
   const openReplace = () => {
@@ -154,7 +158,11 @@ export default function ExpenseWorkflow({
     if (expense) {
       setDescription(expense.description);
       setCategoryId(expense.category_id);
-      setAmount(unitAdapter.toDisplay(expense.amount_minor / minorFactor));
+      setAmount(
+        expense.amount_minor === null
+          ? ''
+          : unitAdapter.toDisplay(expense.amount_minor / minorFactor),
+      );
       setIncurredOn(expense.incurred_on);
       setPayee(expense.payee ?? '');
       setNotes(expense.notes ?? '');
@@ -409,7 +417,7 @@ export default function ExpenseWorkflow({
       focusAmount();
       return;
     }
-    if (cents > record.due_minor) {
+    if (record.due_minor === null || cents > record.due_minor) {
       setErrors({ amount: t('exceedsDue', { amount: fmtMinor(record.due_minor) }) });
       focusAmount();
       return;
@@ -1038,9 +1046,7 @@ export default function ExpenseWorkflow({
                   <Button
                     type="button"
                     onClick={openPayment}
-                    disabled={
-                      busy || locked || record.status !== 'active' || record.due_minor === 0
-                    }
+                    disabled={busy || locked || record.status !== 'active' || !record.due_minor}
                     data-testid="expense-record-payment"
                   >
                     {t('paymentTitle')}

frontend/src/lib/types.ts

@@ -358,7 +358,7 @@ export interface ExpenseRecord {
   description: string;
   payee: string | null;
   notes: string | null;
-  amount_minor: number;
+  amount_minor: number | null;
   currency_code: string;
   incurred_on: string;
   created_by: string;
@@ -369,7 +369,7 @@ export interface ExpenseRecord {
   void_reason: string | null;
   status: ExpenseStatus;
   paid_minor: number;
-  due_minor: number;
+  due_minor: number | null;
 }
 
 export interface ExpensePaymentRecord {