feat(targets): price target/stop simulator with chart overlay lines

- New lib/targets.ts: per-code localStorage (key `targets:<code>`) with
  read/write/clear; rejects non-positive/non-finite values.
- New PriceTargets sidebar panel: 목표가/손절가 inputs, live %-from-current
  preview (rose=up, sky=down), save/clear actions.
- StockChart accepts optional `targets` prop and draws dashed horizontal
  price lines on the candle series (rose=target, sky=stop) with axis labels.
- Page loads saved targets on mount/code-change and re-renders chart on save.

Also fixes view-counter dedupe caveat from reviewer: split into
wasRecordedToday() + markRecorded(); the page now marks localStorage only
after POST /api/views succeeds, so a failed POST stays retryable on the
next visit instead of being silently swallowed for the day.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/lib/views.ts

@@ -38,11 +38,17 @@ function writeLogged(m: LoggedMap): void {
   }
 }
 
-/** 오늘 처음 보는 code 면 true, 이미 봤으면 false. true 인 경우 mark 까지 수행. */
-export function shouldRecordView(code: string): boolean {
+/** 오늘 이미 카운트된 종목인지. POST 호출 전 dedupe 게이트. */
+export function wasRecordedToday(code: string): boolean {
+  const today = kstToday();
+  const logged = readLogged();
+  return logged[code] === today;
+}
+
+/** POST 성공 이후 호출. 실패 시 마크하지 않아 다음 방문에 재시도 가능. */
+export function markRecorded(code: string): void {
   const today = kstToday();
   const logged = readLogged();
-  if (logged[code] === today) return false;
   logged[code] = today;
   // 한도: 너무 커지면 오래된 항목 제거. 단순히 100개로 잘라냄.
   const entries = Object.entries(logged);
@@ -52,5 +58,4 @@ export function shouldRecordView(code: string): boolean {
   } else {
     writeLogged(logged);
   }
-  return true;
 }