feat: enhance chart tooltip and legend components with improved type definitions and payload handling

lib/ofx-parser.tsx

@@ -42,7 +42,7 @@ export function parseOFX(content: string): OFXAccount | null {
         amount: Number.parseFloat(amountStr),
         name: cleanString(name),
         memo: memo ? cleanString(memo) : undefined,
-        checkNum,
+        checkNum: checkNum ?? undefined,
         type,
       })
     }