refactor(signals): drop the now-unused fmtMoney helper

It was lifted from BacktestPanel during the extraction, then lost its last
caller in the same branch when avg_trade_pnl became an EV / trade tile rendered
with fmtSignedMoney and disappeared from the monitor footnote. formatPrice
already covers a bare unsigned amount if one is ever needed again.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/lib/format.ts

@@ -110,21 +110,10 @@ export function fmtRatio(v: number | null | undefined): string {
   return v === null || v === undefined ? '—' : v.toFixed(2);
 }
 
-/**
- * Bare amount, no currency symbol and no sign. e.g. 1234.5 → "1,234.50"
- * Kept separate from fmtSignedMoney on purpose — they are not interchangeable.
- */
-export function fmtMoney(v: number | null | undefined): string {
-  if (v === null || v === undefined) return '—';
-  return v.toLocaleString('en-US', {
-    minimumFractionDigits: 2,
-    maximumFractionDigits: 2,
-  });
-}
-
 /**
  * Signed currency, using U+2212 for negatives. e.g. -12.3 → "−$12.30"
  * Use wherever a value can go negative and the unit is money.
+ * (For a bare unsigned amount there is already `formatPrice` above.)
  */
 export function fmtSignedMoney(v: number | null | undefined): string {
   if (v === null || v === undefined) return '—';