fix: TS type mismatch in mutation onSubmit handlers

frontend/src/components/AddMoneyDialog.tsx

@@ -9,7 +9,7 @@ interface AddMoneyDialogProps {
   bank: PiggyBank | null
   open: boolean
   onOpenChange: (open: boolean) => void
-  onSubmit: (bankId: number, amount: number, description?: string) => Promise<void>
+  onSubmit: (bankId: number, amount: number, description?: string) => Promise<unknown>
 }
 
 export function AddMoneyDialog({ bank, open, onOpenChange, onSubmit }: AddMoneyDialogProps) {

frontend/src/components/PiggyBankForm.tsx

@@ -6,7 +6,7 @@ import { Select } from './ui/select'
 
 interface PiggyBankFormProps {
   categories: Category[]
-  onSubmit: (data: { name: string; target_amount: number; currency: string; category_id: number | null }) => Promise<void>
+  onSubmit: (data: { name: string; target_amount: number; currency: string; category_id: number | null }) => Promise<unknown>
   onCancel: () => void
 }