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/components/PriceTargets.tsx

@@ -0,0 +1,154 @@
+"use client";
+
+// 목표가 / 손절가 시뮬레이터 (Toss "내 목표가" read-only 클론).
+//   - 현재가 기준 변동률 미리 계산해서 표시
+//   - 저장 시 localStorage 에만 — 차트 오버레이는 부모 page 가 같은 상태를 읽어 StockChart 에 전달
+//   - 알림은 별도 AlertsPanel 담당, 여기는 시각화 + 손익 프리뷰만
+
+import { useEffect, useMemo, useState } from "react";
+import { readTargets, writeTargets, type Targets } from "../lib/targets";
+
+type Props = {
+  code: string;
+  current: number | null;
+  // 저장/해제 시 부모에 변경을 전달 — 차트에 즉시 반영하도록.
+  onChange?: (t: Targets) => void;
+};
+
+function parseNum(s: string): number | null {
+  const cleaned = s.replace(/,/g, "").trim();
+  if (!cleaned) return null;
+  const n = Number(cleaned);
+  return Number.isFinite(n) && n > 0 ? n : null;
+}
+
+function pct(price: number | null, current: number | null): number | null {
+  if (price == null || current == null || current <= 0) return null;
+  return ((price - current) / current) * 100;
+}
+
+export function PriceTargets({ code, current, onChange }: Props) {
+  const [target, setTarget] = useState("");
+  const [stop, setStop] = useState("");
+  const [saved, setSaved] = useState<Targets>({});
+
+  // 종목 바뀌면 새로 로드. 입력창도 저장값으로 초기화.
+  useEffect(() => {
+    const t = readTargets(code);
+    setSaved(t);
+    setTarget(t.target != null ? String(t.target) : "");
+    setStop(t.stop != null ? String(t.stop) : "");
+  }, [code]);
+
+  const targetN = useMemo(() => parseNum(target), [target]);
+  const stopN = useMemo(() => parseNum(stop), [stop]);
+  const targetPct = pct(targetN, current);
+  const stopPct = pct(stopN, current);
+
+  const dirty =
+    (targetN ?? null) !== (saved.target ?? null) ||
+    (stopN ?? null) !== (saved.stop ?? null);
+
+  const save = () => {
+    const next: Targets = { target: targetN, stop: stopN };
+    writeTargets(code, next);
+    setSaved(next);
+    onChange?.(next);
+  };
+  const clear = () => {
+    setTarget("");
+    setStop("");
+    const next: Targets = {};
+    writeTargets(code, next);
+    setSaved(next);
+    onChange?.(next);
+  };
+
+  const fmtPct = (p: number | null): string =>
+    p == null ? "" : `${p >= 0 ? "+" : ""}${p.toFixed(2)}%`;
+  const pctCls = (p: number | null): string =>
+    p == null ? "text-zinc-500" : p >= 0 ? "text-rose-400" : "text-sky-400";
+
+  return (
+    <div className="rounded-lg border border-zinc-800 bg-zinc-900/40 p-3">
+      <div className="mb-2 flex items-baseline justify-between">
+        <h3 className="text-xs font-semibold text-zinc-300">내 목표가</h3>
+        <span className="text-[10px] text-zinc-500">브라우저 저장 · 비공개</span>
+      </div>
+      <div className="space-y-2">
+        <Row
+          label="목표가"
+          color="bg-rose-400/80"
+          value={target}
+          onChange={setTarget}
+          deltaText={fmtPct(targetPct)}
+          deltaCls={pctCls(targetPct)}
+        />
+        <Row
+          label="손절가"
+          color="bg-sky-400/80"
+          value={stop}
+          onChange={setStop}
+          deltaText={fmtPct(stopPct)}
+          deltaCls={pctCls(stopPct)}
+        />
+      </div>
+      <div className="mt-2 flex items-center gap-2">
+        <button
+          type="button"
+          onClick={save}
+          disabled={!dirty}
+          className="flex-1 rounded-md border border-zinc-700 bg-zinc-800/80 px-2 py-1 text-[11px] text-zinc-100 transition hover:border-zinc-500 disabled:cursor-not-allowed disabled:opacity-40"
+        >
+          저장
+        </button>
+        <button
+          type="button"
+          onClick={clear}
+          disabled={saved.target == null && saved.stop == null && !target && !stop}
+          className="rounded-md border border-zinc-800 px-2 py-1 text-[11px] text-zinc-400 transition hover:border-zinc-600 hover:text-zinc-200 disabled:cursor-not-allowed disabled:opacity-40"
+        >
+          해제
+        </button>
+      </div>
+      {current == null && (
+        <div className="mt-1 text-[10px] text-zinc-500">현재가 로딩 중 — 변동률은 잠시 후 표시</div>
+      )}
+    </div>
+  );
+}
+
+function Row({
+  label,
+  color,
+  value,
+  onChange,
+  deltaText,
+  deltaCls,
+}: {
+  label: string;
+  color: string;
+  value: string;
+  onChange: (s: string) => void;
+  deltaText: string;
+  deltaCls: string;
+}) {
+  return (
+    <label className="flex items-center gap-2 text-[11px]">
+      <span className={`inline-block h-2 w-2 rounded-sm ${color}`} aria-hidden />
+      <span className="w-12 shrink-0 text-zinc-400">{label}</span>
+      <input
+        type="text"
+        inputMode="numeric"
+        autoComplete="off"
+        value={value}
+        onChange={(e) => onChange(e.target.value)}
+        placeholder="0"
+        className="min-w-0 flex-1 rounded border border-zinc-800 bg-zinc-950/50 px-2 py-1 text-right tabular-nums text-zinc-100 outline-none focus:border-zinc-600"
+      />
+      <span className={`w-16 shrink-0 text-right tabular-nums ${deltaCls}`}>
+        {deltaText}
+      </span>
+    </label>
+  );
+}

web/components/StockChart.tsx

@@ -6,6 +6,7 @@ import {
   type CandlestickData,
   type HistogramData,
   type IChartApi,
+  type IPriceLine,
   type ISeriesApi,
   type LineData,
   type LogicalRange,
@@ -13,10 +14,13 @@ import {
   type UTCTimestamp,
 } from "lightweight-charts";
 import type { ChartPayload, LatestPredictionResponse } from "../lib/api";
+import type { Targets } from "../lib/targets";
 
 type Props = {
   chart: ChartPayload;
   prediction?: LatestPredictionResponse | null;
+  // 사용자가 저장한 목표가/손절가 — 메인 캔들 위 가로 라인 오버레이.
+  targets?: Targets | null;
 };
 
 // KST naive ISO ('YYYY-MM-DD' 또는 'YYYY-MM-DDTHH:MM:SS') 를 UTCTimestamp 로.
@@ -198,7 +202,7 @@ function macd(
   return { macd: m, signal: sig, hist };
 }
 
-export function StockChart({ chart, prediction }: Props) {
+export function StockChart({ chart, prediction, targets }: Props) {
   const containerRef = useRef<HTMLDivElement | null>(null);
   const chartRef = useRef<IChartApi | null>(null);
   const candleRef = useRef<ISeriesApi<"Candlestick"> | null>(null);
@@ -215,6 +219,9 @@ export function StockChart({ chart, prediction }: Props) {
   const macdLineRef = useRef<ISeriesApi<"Line"> | null>(null);
   const macdSignalRef = useRef<ISeriesApi<"Line"> | null>(null);
   const macdHistRef = useRef<ISeriesApi<"Histogram"> | null>(null);
+  // 목표가/손절가 가로 라인 — candleRef 의 priceLine 으로 부착.
+  const targetLineRef = useRef<IPriceLine | null>(null);
+  const stopLineRef = useRef<IPriceLine | null>(null);
 
   // 보조 차트 crosshair 동기화용 time→value lookup.
   // 메인 차트에서 hover 한 시점의 RSI/MACD 값을 O(1) 로 찾아 setCrosshairPosition 에
@@ -430,6 +437,43 @@ export function StockChart({ chart, prediction }: Props) {
     chartRef.current.timeScale().fitContent();
   }, [prediction, isIntraday]);
 
+  // 목표가/손절가 가로 라인 — targets prop 또는 캔들 시리즈 재생성 시 동기화.
+  // candleRef 가 바뀌면 이전 라인 ref 는 이미 해제된 상태라 그냥 새로 만들면 됨.
+  useEffect(() => {
+    const candle = candleRef.current;
+    if (!candle) return;
+    // 이전 라인 제거 후 새로 그림 — 입력 바뀔 때마다 가격값 변경하지 않고 그냥 재생성.
+    if (targetLineRef.current) {
+      try { candle.removePriceLine(targetLineRef.current); } catch { /* 이미 해제됨 */ }
+      targetLineRef.current = null;
+    }
+    if (stopLineRef.current) {
+      try { candle.removePriceLine(stopLineRef.current); } catch { /* 이미 해제됨 */ }
+      stopLineRef.current = null;
+    }
+    if (!targets) return;
+    if (targets.target != null && Number.isFinite(targets.target)) {
+      targetLineRef.current = candle.createPriceLine({
+        price: targets.target,
+        color: "#fb7185",        // rose-400 (한국 상승색 톤)
+        lineWidth: 1,
+        lineStyle: 2,            // dashed
+        axisLabelVisible: true,
+        title: "목표",
+      });
+    }
+    if (targets.stop != null && Number.isFinite(targets.stop)) {
+      stopLineRef.current = candle.createPriceLine({
+        price: targets.stop,
+        color: "#60a5fa",        // sky-400 (한국 하락색 톤)
+        lineWidth: 1,
+        lineStyle: 2,
+        axisLabelVisible: true,
+        title: "손절",
+      });
+    }
+  }, [targets, isIntraday]);
+
   // RSI 보조 차트 생성/제거 — toggle 또는 interval 변경 시. 메인 chart 와 별 인스턴스.
   // priceScale fix (0-100) + 30/70 가이드 라인.
   useEffect(() => {