Reapply "Add missing admin action files and navigation links"

This reverts commit 4d515bc400.

src/app/admin/settings/page.tsx

@@ -42,14 +42,19 @@ export default async function AdminSettings() {
             <input name="key" placeholder={t("form.keyPlaceholder")} required />
             <input name="value" placeholder={t("form.valuePlaceholder")} className="flex-1 min-w-[160px]" />
             <input name="comment" placeholder={t("form.commentPlaceholder")} />
-            <button type="submit" className="btn btn-primary">{t("save")}</button>
+            <button type="submit" className="btn btn-primary">
+              {t("save")}
+            </button>
           </div>
         </form>
       </section>
 
       <section>
         <h2 className="admin-section-title">
-          {t("settings")} <span className="inline-block text-[0.72rem] font-bold px-2 py-0.5 rounded-full bg-[var(--color-primary)]/18 text-[var(--color-text)]">{settings.length}</span>
+          {t("settings")}{" "}
+          <span className="inline-block text-[0.72rem] font-bold px-2 py-0.5 rounded-full bg-[var(--color-primary)]/18 text-[var(--color-text)]">
+            {settings.length}
+          </span>
         </h2>
         {settings.length === 0 ? (
           <div className="admin-empty">{t("noSettings")}</div>
@@ -59,10 +64,7 @@ export default async function AdminSettings() {
               <div key={s.key} className="admin-card">
                 <div style={{ display: "flex", gap: "0.75rem", alignItems: "baseline" }}>
                   <strong style={{ minWidth: 220 }}>{s.key}</strong>
-                  <form
-                    action={updateSetting}
-                    style={{ display: "flex", gap: "0.5rem", flex: 1 }}
-                  >
+                  <form action={updateSetting} style={{ display: "flex", gap: "0.5rem", flex: 1 }}>
                     <input type="hidden" name="key" value={s.key} />
                     <input name="value" defaultValue={s.value} style={{ flex: 1 }} />
                     <button type="submit" className="btn btn-outline">