refactor: replace ignored numeric literals with constants

src/integrations/tbank/decimal.ts

@@ -1,12 +1,14 @@
 import { Decimal } from '../../common/decimal';
 
+const MISSING_PROTO_COMPONENT = 0;
+
 const NANO = 1_000_000_000n;
 
 export type ProtoDecimal = { nano?: number | string; units?: number | string };
 
 export function decimal(value: ProtoDecimal): Decimal {
   return {
-    value: BigInt(value.units ?? 0) * NANO + BigInt(value.nano ?? 0),
+    value: BigInt(value.units ?? MISSING_PROTO_COMPONENT) * NANO + BigInt(value.nano ?? MISSING_PROTO_COMPONENT),
     scale: 9,
   };
 }