Show Tailscale device key expiry

Tailscale node keys expire (180 days by default unless disabled per
device) and an expired key drops the device off the tailnet until
re-authenticated -- worth surfacing before it happens.

adapter.listDevices() now reads `expires` and `keyExpiryDisabled` from
the device list API (`?fields=all`, already being fetched). Go's zero
time ("0001-01-01T00:00:00Z") is what Tailscale returns for "no real
expiry set" and is treated as null rather than shown as a bogus 1AD
date.

New "Key expiry" column on the Tailscale page: "Never" when disabled,
otherwise the date plus a badge (green/yellow/red matching the
Secrets module's ok/expiring/expired convention) using the same
30-day warning window as that module's default. The devices summary
gained `expiringSoon` (<=30 days left, including already-expired),
surfaced in the page header and as a new warning line on the
Dashboard's Tailscale widget, alongside the existing "awaiting
authorization" one.

Verified the parsing (real expiry, disabled/zero-time, already-expired,
far-future) against the compiled adapter with fetch calls to
api.tailscale.com redirected to a local mock server, since this
sandbox can't reach the user's real tailnet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/api/client.ts

@@ -310,11 +310,13 @@ export interface TailscaleDevice {
   isExitNode: boolean;
   authorized: boolean;
   online: boolean;
+  keyExpiry: string | null;
+  keyExpiryDisabled: boolean;
 }
 
 export interface TailscaleDevicesResponse {
   devices: TailscaleDevice[];
-  summary: { total: number; online: number; unauthorized: number };
+  summary: { total: number; online: number; unauthorized: number; expiringSoon: number };
 }
 
 export interface GiteaWorkflowRun {

web/src/pages/Dashboard.tsx

@@ -181,6 +181,9 @@ export default function Dashboard({ user }: { user: CurrentUser }) {
                       {tailscaleSummary!.unauthorized > 0 && (
                         <div className="text-yellow small mt-1">{tailscaleSummary!.unauthorized} awaiting authorization</div>
                       )}
+                      {tailscaleSummary!.expiringSoon > 0 && (
+                        <div className="text-yellow small mt-1">{tailscaleSummary!.expiringSoon} key(s) expiring soon</div>
+                      )}
                     </div>
                   ) : isLiveGitea ? (
                     <div className="mt-2">

web/src/pages/Tailscale.tsx

@@ -9,6 +9,22 @@ import {
 } from "../api/client";
 import { formatDateTime } from "../utils/date";
 
+const KEY_EXPIRY_WARN_DAYS = 30;
+
+function keyExpiryBadge(device: TailscaleDevice) {
+  if (device.keyExpiryDisabled || !device.keyExpiry) {
+    return <span className="text-secondary">Never</span>;
+  }
+  const daysLeft = (new Date(device.keyExpiry).getTime() - Date.now()) / 86_400_000;
+  const style =
+    daysLeft < 0 ? "bg-red-lt text-red" : daysLeft <= KEY_EXPIRY_WARN_DAYS ? "bg-yellow-lt text-yellow" : "bg-green-lt text-green";
+  return (
+    <>
+      {formatDateTime(new Date(device.keyExpiry))} <span className={`badge ${style} ms-1`}>{daysLeft < 0 ? "Expired" : `${Math.floor(daysLeft)}d left`}</span>
+    </>
+  );
+}
+
 export default function Tailscale({ user }: { user: CurrentUser }) {
   const canEdit = user.role === "admin" || user.role === "operator";
 
@@ -120,6 +136,7 @@ export default function Tailscale({ user }: { user: CurrentUser }) {
                     <span className="text-secondary fw-normal ms-2">
                       {data.summary.online}/{data.summary.total} online
                       {data.summary.unauthorized > 0 && `, ${data.summary.unauthorized} awaiting authorization`}
+                      {data.summary.expiringSoon > 0 && `, ${data.summary.expiringSoon} key(s) expiring soon`}
                     </span>
                   )}
                 </h3>
@@ -142,6 +159,7 @@ export default function Tailscale({ user }: { user: CurrentUser }) {
                       <th>OS</th>
                       <th>Status</th>
                       <th>Last seen</th>
+                      <th>Key expiry</th>
                       {canEdit && <th className="w-1">Actions</th>}
                     </tr>
                   </thead>
@@ -163,6 +181,7 @@ export default function Tailscale({ user }: { user: CurrentUser }) {
                           {!d.authorized && <span className="badge bg-yellow-lt text-yellow">Unauthorized</span>}
                         </td>
                         <td className="text-secondary">{d.lastSeen ? formatDateTime(new Date(d.lastSeen)) : "—"}</td>
+                        <td>{keyExpiryBadge(d)}</td>
                         {canEdit && (
                           <td>
                             <div className="btn-list flex-nowrap">
@@ -185,7 +204,7 @@ export default function Tailscale({ user }: { user: CurrentUser }) {
                     ))}
                     {data?.devices.length === 0 && (
                       <tr>
-                        <td colSpan={canEdit ? 6 : 5} className="text-secondary text-center">
+                        <td colSpan={canEdit ? 7 : 6} className="text-secondary text-center">
                           No devices in this tailnet.
                         </td>
                       </tr>