fix(settings): bank accounts saved blank — flatten payload + harden schema to strictObject

The bank form posted {id, bank:{...}} (nested) but the route/schema read fields
at the top level; lenient z.object silently stripped the wrapper, so every field
saved as null while returning success. Flatten the payload to top level and switch
the create/update schemas to strictObject so a future nesting 400s loudly instead
of saving a blank record. Affects both create and edit.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/CompanySettings.tsx

@@ -241,7 +241,7 @@ export default function CompanySettings({
   });
 
   const bankMutation = useApiMutation<
-    { id?: number; bank: BankForm },
+    BankForm & { id?: number },
     { message?: string }
   >({
     url: (input) =>
@@ -432,8 +432,8 @@ export default function CompanySettings({
     setBankSaving(true);
     try {
       const result = await bankMutation.mutateAsync({
+        ...bankForm,
         id: editingBank ?? undefined,
-        bank: bankForm,
       });
       alert.success(result?.message || "Uloženo");
       resetBankForm();