feat(archive): implement sortable columns in archive table with toggle functionality

frontend/src/index.css

@@ -530,6 +530,16 @@ kbd {
   background: rgba(255,255,255,0.04);
   border: 1px solid rgba(255,255,255,0.08);
 }
+.archive-head-btn {
+  all: unset;
+  cursor: pointer;
+  font-weight: 800;
+  color: var(--subtle);
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+}
+.archive-head-btn:hover { color: var(--text); }
 .archive-row {
   background: rgba(255,255,255,0.03);
   border: 1px solid rgba(255,255,255,0.05);

frontend/src/pages/ArchivePage.tsx

@@ -5,6 +5,9 @@ import { useAuth } from "../auth/AuthProvider";
 import { toastError } from "../utils/toastBus";
 import { logApiError } from "../utils/logger";
 
+type SortKey = "id" | "ep_num" | "ep_title" | "season_name" | "start_time" | "playback_length" | "date_created" | "date_archived";
+type SortDir = "asc" | "desc" | null;
+
 function formatTimestamp(ts: string) {
     if (!ts) return "";
     const d = new Date(ts);
@@ -17,6 +20,7 @@ export default function ArchivePage() {
     const [items, setItems] = React.useState<ArchiveItem[]>([]);
     const [loading, setLoading] = React.useState(true);
     const [error, setError] = React.useState<string | null>(null);
+    const [sort, setSort] = React.useState<{ key: SortKey | null; dir: SortDir }>({ key: null, dir: null });
 
     const load = React.useCallback(async () => {
         if (!idToken) {
@@ -46,6 +50,51 @@ export default function ArchivePage() {
         }
     }, [enabled, isAdmin, idToken, load]);
 
+    const sortedItems = React.useMemo(() => {
+        const { key, dir } = sort;
+        if (!key || !dir) return items;
+        const next = [...items];
+        next.sort((a, b) => {
+            let av: string | number = "";
+            let bv: string | number = "";
+            switch (key) {
+                case "id":
+                case "ep_num":
+                    av = a[key];
+                    bv = b[key];
+                    break;
+                case "date_created":
+                case "date_archived":
+                    av = new Date(a[key]).getTime();
+                    bv = new Date(b[key]).getTime();
+                    break;
+                default:
+                    av = (a as Record<string, unknown>)[key] as string | number | undefined ?? "";
+                    bv = (b as Record<string, unknown>)[key] as string | number | undefined ?? "";
+            }
+            if (av === bv) return 0;
+            const asc = av > bv ? 1 : -1;
+            return dir === "asc" ? asc : -asc;
+        });
+        return next;
+    }, [items, sort]);
+
+    function toggleSort(key: SortKey) {
+        setSort((prev) => {
+            if (prev.key !== key) return { key, dir: "asc" };
+            if (prev.dir === "asc") return { key, dir: "desc" };
+            if (prev.dir === "desc") return { key: null, dir: null };
+            return { key, dir: "asc" };
+        });
+    }
+
+    const sortIndicator = (key: SortKey) => {
+        if (sort.key !== key) return "";
+        if (sort.dir === "asc") return "▲";
+        if (sort.dir === "desc") return "▼";
+        return "";
+    };
+
     if (!enabled) {
         return <div className="subtle">認証が無効です。</div>;
     }
@@ -77,16 +126,32 @@ export default function ArchivePage() {
                 <div className="archive-scroll">
                     <div className="archive-table">
                         <div className="archive-header">
-                            <span>ID</span>
-                            <span>話数</span>
-                            <span>タイトル</span>
-                            <span>シーズン</span>
-                            <span>開始時刻</span>
-                            <span>再生時間</span>
-                            <span>登録</span>
-                            <span>アーカイブ</span>
+                            <button className="archive-head-btn" onClick={() => toggleSort("id")}>
+                                ID {sortIndicator("id")}
+                            </button>
+                            <button className="archive-head-btn" onClick={() => toggleSort("ep_num")}>
+                                話数 {sortIndicator("ep_num")}
+                            </button>
+                            <button className="archive-head-btn" onClick={() => toggleSort("ep_title")}>
+                                タイトル {sortIndicator("ep_title")}
+                            </button>
+                            <button className="archive-head-btn" onClick={() => toggleSort("season_name")}>
+                                シーズン {sortIndicator("season_name")}
+                            </button>
+                            <button className="archive-head-btn" onClick={() => toggleSort("start_time")}>
+                                開始時刻 {sortIndicator("start_time")}
+                            </button>
+                            <button className="archive-head-btn" onClick={() => toggleSort("playback_length")}>
+                                再生時間 {sortIndicator("playback_length")}
+                            </button>
+                            <button className="archive-head-btn" onClick={() => toggleSort("date_created")}>
+                                登録 {sortIndicator("date_created")}
+                            </button>
+                            <button className="archive-head-btn" onClick={() => toggleSort("date_archived")}>
+                                アーカイブ {sortIndicator("date_archived")}
+                            </button>
                         </div>
-                        {items.map((it) => (
+                        {sortedItems.map((it) => (
                             <div key={it.id} className="archive-row">
                                 <span>#{it.id}</span>
                                 <span>第{it.ep_num}話</span>