Schedule chips: horizontal scroll with edge arrows (PC navigable)

Replace hidden-scrollbar row (inaccessible on desktop without touch) with
a ChipScroller: single-row scroll + left/right arrow buttons that auto-hide
at each end and a bg fade. Resets to start on tab switch.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/ScheduleBoard.tsx

@@ -1,4 +1,4 @@
-import { useMemo, useState } from "react";
+import { useEffect, useLayoutEffect, useMemo, useRef, useState } from "react";
 import { Link } from "react-router-dom";
 import { timeOnly, dateKey } from "@/lib/format";
 import { type Lang, dict, teamShort, roundLabel as tRound, dayName, monthEn } from "@/lib/i18n";
@@ -90,8 +90,8 @@ export default function ScheduleBoard({
         ))}
       </div>
 
-      {/* 칩: 날짜 또는 조 */}
+      {/* 칩: 날짜 또는 조 — 단일 줄 가로 스크롤 + 양 끝 화살표(PC에서 마우스로 넘김, 끝 도달 시 숨김) */}
-      <div className="mb-4 flex gap-2 overflow-x-auto pb-1 [scrollbar-width:none] [&::-webkit-scrollbar]:hidden">
+      <ChipScroller resetKey={tab}>
         {tab === "date"
           ? dates.map((d) => (
               <Chip key={d} active={d === selDate} onClick={() => setSelDate(d)}>
@@ -103,7 +103,7 @@ export default function ScheduleBoard({
                 {lang === "en" ? `Group ${g}` : `${g}조`}
               </Chip>
             ))}
-      </div>
+      </ChipScroller>
 
       {/* 경기 카드 */}
       <div className="flex flex-col gap-2.5">
@@ -120,6 +120,86 @@ export default function ScheduleBoard({
   );
 }
 
+// 단일 줄 가로 스크롤 + 양 끝 화살표. 끝에 닿으면 해당 방향 화살표를 숨긴다.
+// resetKey 가 바뀌면(탭 전환 등) 맨 앞으로 되감고 재측정한다.
+function ChipScroller({
+  children,
+  resetKey,
+}: {
+  children: React.ReactNode;
+  resetKey?: string | number;
+}) {
+  const ref = useRef<HTMLDivElement>(null);
+  const [atStart, setAtStart] = useState(true);
+  const [atEnd, setAtEnd] = useState(true);
+
+  const measure = () => {
+    const el = ref.current;
+    if (!el) return;
+    const max = el.scrollWidth - el.clientWidth;
+    setAtStart(el.scrollLeft <= 1);
+    setAtEnd(el.scrollLeft >= max - 1);
+  };
+
+  // 탭/목록 변경 시 맨 앞으로 + 재측정 (레이아웃 확정 후)
+  useLayoutEffect(() => {
+    const el = ref.current;
+    if (el) el.scrollLeft = 0;
+    measure();
+  }, [resetKey]);
+
+  useEffect(() => {
+    measure();
+    const el = ref.current;
+    if (!el) return;
+    el.addEventListener("scroll", measure, { passive: true });
+    window.addEventListener("resize", measure);
+    return () => {
+      el.removeEventListener("scroll", measure);
+      window.removeEventListener("resize", measure);
+    };
+  }, []);
+
+  const nudge = (dir: 1 | -1) =>
+    ref.current?.scrollBy({ left: dir * 220, behavior: "smooth" });
+
+  return (
+    <div className="relative mb-4">
+      <div
+        ref={ref}
+        className="flex gap-2 overflow-x-auto pb-1 [scrollbar-width:none] [&::-webkit-scrollbar]:hidden"
+      >
+        {children}
+      </div>
+
+      {!atStart && (
+        <div className="pointer-events-none absolute inset-y-0 left-0 flex items-center pr-8 bg-gradient-to-r from-[var(--bg)] via-[var(--bg)] to-transparent">
+          <button
+            type="button"
+            aria-label="이전"
+            onClick={() => nudge(-1)}
+            className="pointer-events-auto grid h-7 w-7 place-items-center rounded-full border border-[var(--line-d)] bg-[var(--bg2)] text-[15px] leading-none text-white/80 shadow transition hover:text-white active:scale-95"
+          >
+            ‹
+          </button>
+        </div>
+      )}
+      {!atEnd && (
+        <div className="pointer-events-none absolute inset-y-0 right-0 flex items-center justify-end pl-8 bg-gradient-to-l from-[var(--bg)] via-[var(--bg)] to-transparent">
+          <button
+            type="button"
+            aria-label="다음"
+            onClick={() => nudge(1)}
+            className="pointer-events-auto grid h-7 w-7 place-items-center rounded-full border border-[var(--line-d)] bg-[var(--bg2)] text-[15px] leading-none text-white/80 shadow transition hover:text-white active:scale-95"
+          >
+            ›
+          </button>
+        </div>
+      )}
+    </div>
+  );
+}
+
 function Chip({
   active,
   onClick,