fix: recover expired dashboard sessions (#309)

frontend/login.js

@@ -11,6 +11,11 @@
   const clearIntervalImpl = options.clearIntervalImpl || clearInterval;
   let timer = null;
 
+  function showReason(reason) {
+    if (reason !== 'session-expired') return;
+    status.textContent = 'Your session expired. Private drafts remain on this device. Sign in to continue.';
+  }
+
   function showRetryCountdown(seconds) {
     let remaining = Math.max(1, Number.parseInt(seconds, 10) || 1);
     button.disabled = true;
@@ -54,7 +59,7 @@
     status.textContent = 'Sign-in failed. Check the token and try again.';
   }
 
-  return { submit };
+  return { submit, showReason };
 }));
 
 if (typeof document !== 'undefined') {
@@ -68,6 +73,7 @@ if (typeof document !== 'undefined') {
     fetchImpl: fetch.bind(window),
     location: window.location,
   });
+  controller.showReason(new URLSearchParams(window.location.search).get('reason'));
   form.addEventListener('submit', event => {
     event.preventDefault();
     const accessToken = new FormData(form).get('access_token');

frontend/service-worker.js

@@ -1,6 +1,6 @@
 const BASE = new URL('./', self.location.href).pathname;
 importScripts(BASE + 'static/background-issue-sync.js');
-const CACHE = 'stackchain-dashboard-shell-v30';
+const CACHE = 'stackchain-dashboard-shell-v31';
 const OUTAGE_STATUSES = new Set([500, 502, 503, 504]);
 const SHELL = [
   BASE,

frontend/session.js

@@ -40,6 +40,7 @@
   onClearError = () => {},
 }) {
   const SAFE_METHODS = new Set(['GET', 'HEAD', 'OPTIONS']);
+  let expirationStarted = false;
 
   function csrfToken() {
     const entry = String(cookie?.() || '').split(';')
@@ -63,7 +64,11 @@
       requestOptions.headers = headers;
     }
     const response = await fetchImpl(input, requestOptions);
-    if (response.status === 401) onExpired();
+    if (response.status === 401 && isSameOrigin(input) && !expirationStarted) {
+      expirationStarted = true;
+      onExpired();
+      location.replace(base + 'login?reason=session-expired');
+    }
     return response;
   }