feat: expand redeem duration options (hours/days/months/year)

- Add 6h, 12h, 1d, 3d, 7d, 14d, 1mo, 3mo, 6mo, 1yr presets
- Add formatDuration helper for smart display (分钟/小时/天/月/年)
- Fix custom value handling when editing items with non-preset durations

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/app/admin-redeem/page.tsx

@@ -62,6 +62,23 @@ function fmtTs(v: number | null | undefined): string {
   return new Date(v * 1000).toLocaleString();
 }
 
+function formatDuration(mins: number): string {
+  if (mins >= 525600) {
+    const y = mins / 525600;
+    return Number.isInteger(y) ? `${y}年` : `${(mins / 1440).toFixed(0)}天`;
+  }
+  if (mins >= 43200) {
+    const m = mins / 43200;
+    return Number.isInteger(m) ? `${m}个月` : `${(mins / 1440).toFixed(0)}天`;
+  }
+  if (mins >= 1440) return `${(mins / 1440).toFixed(0)}天`;
+  if (mins >= 60) {
+    const h = mins / 60;
+    return Number.isInteger(h) ? `${h}小时` : `${h.toFixed(1)}小时`;
+  }
+  return `${mins}分钟`;
+}
+
 export default function AdminRedeemPage() {
   const { tx } = useI18nText();
   const [token, setToken] = useState("");
@@ -224,7 +241,12 @@ export default function AdminRedeemPage() {
           <div className="flex items-center gap-2">
             <select
               className="rounded border px-3 py-2 text-sm flex-1"
-              value={form.duration_minutes === 0 ? "0" : String(form.duration_minutes)}
+              value={
+                form.duration_minutes === 0 ? "0"
+                : form.duration_minutes === -1 ? "-1"
+                : [15,30,60,90,120,180,360,720,1440,4320,10080,20160,43200,129600,259200,525600].includes(form.duration_minutes)
+                  ? String(form.duration_minutes) : "-1"
+              }
               onChange={(e) => setForm((prev) => ({ ...prev, duration_minutes: Number(e.target.value) }))}
             >
               <option value="0">{tx("永久有效 ♾️", "Permanent ♾️")}</option>
@@ -234,14 +256,25 @@ export default function AdminRedeemPage() {
               <option value="90">1.5 {tx("小时", "hours")}</option>
               <option value="120">2 {tx("小时", "hours")}</option>
               <option value="180">3 {tx("小时", "hours")}</option>
+              <option value="360">6 {tx("小时", "hours")}</option>
+              <option value="720">12 {tx("小时", "hours")}</option>
+              <option value="1440">1 {tx("天", "day")}</option>
+              <option value="4320">3 {tx("天", "days")}</option>
+              <option value="10080">7 {tx("天", "days")}</option>
+              <option value="20160">14 {tx("天", "days")}</option>
+              <option value="43200">1 {tx("个月", "month")}</option>
+              <option value="129600">3 {tx("个月", "months")}</option>
+              <option value="259200">6 {tx("个月", "months")}</option>
+              <option value="525600">1 {tx("年", "year")}</option>
               <option value="-1">{tx("自定义", "Custom")}</option>
             </select>
-            {form.duration_minutes === -1 && (
+            {(form.duration_minutes === -1 || (form.duration_minutes > 0 && ![15,30,60,90,120,180,360,720,1440,4320,10080,20160,43200,129600,259200,525600].includes(form.duration_minutes))) && (
               <input
                 className="rounded border px-3 py-2 text-sm w-24"
                 type="number"
                 min={1}
                 placeholder={tx("分钟", "min")}
+                defaultValue={form.duration_minutes > 0 ? form.duration_minutes : ""}
                 onChange={(e) => {
                   const v = Math.max(1, Number(e.target.value) || 1);
                   setForm((prev) => ({ ...prev, duration_minutes: v }));
@@ -325,9 +358,7 @@ export default function AdminRedeemPage() {
                 {item.unit_label}
                 {" · "}
                 {item.duration_minutes > 0
-                  ? (item.duration_minutes >= 60
-                    ? `⏱️ ${item.duration_minutes / 60}${tx("小时", "h")}`
-                    : `⏱️ ${item.duration_minutes}${tx("分钟", "min")}`)
+                  ? `⏱️ ${formatDuration(item.duration_minutes)}`
                   : `♾️ ${tx("永久", "Permanent")}`}
               </p>
               <p className="text-xs text-zinc-600">