Fix theme consistency, i18n completeness, CSS variable naming, and hardcoded strings

src/app/admin/calendar/[id]/page.tsx

@@ -137,7 +137,7 @@ export default async function AdminCalendarCampaign({
           </thead>
           <tbody>
             {rewards.map((r) => (
-              <tr key={r.id} className="border-t border-[var(--border)]">
+              <tr key={r.id} className="border-t border-[var(--border-subtle)]">
                 <td>{r.id}</td>
                 <td>{r.productName || <span className="text-sm text-gray-500 dark:text-gray-400">—</span>}</td>
                 <td className="text-sm text-gray-500 dark:text-gray-400 whitespace-nowrap">{r.itemId > 0 ? r.itemId : "—"}</td>

src/app/admin/calendar/page.tsx

@@ -83,7 +83,7 @@ export default async function AdminCalendar() {
       {campaigns.length === 0 ? (
         <div className="admin-empty">{t("noCampaigns")}</div>
       ) : (
-        <div className="grid cols-3">
+        <div className="grid grid-cols-1 gap-4 md:grid-cols-3">
           {campaigns.map((c) => {
             const enabled = c.enabled === "1";
             const count = rewardCounts.get(c.id) ?? 0;