webui: reload page on reconnect -> /login

When we reconnect to a device we should reload the page instead of
silently resume.  Because the device may have been rebooted from the
CLI or experienced power loss.  Either way, our session in RAM only
is likely gone, and if so we'll be redirected to /login again.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/webui/static/js/app.js

@@ -68,14 +68,25 @@
       tickerId = setInterval(tick, 1000);
     }
 
-    function hide() {
-      banner.hidden = true;
-      banner.textContent = 'Device unreachable';
-      firstFailureMs = null;
+    // Reconnect: the device is answering again after a disconnect.  It may
+    // have rebooted or been upgraded out of band, in which case
+    // running-config reverted to startup (activated-but-unsaved changes
+    // are gone), operational data is stale, and the in-memory session may
+    // no longer exist.  So we do NOT resume the page the user was on —
+    // we reload it.  A live session re-fetches true post-reboot state; a
+    // dead one makes the server 303-redirect the navigation to /login.
+    // The watchdog only fires `show()` after a >=5 s outage, so this never
+    // triggers on a sub-second blip — only on outages long enough to
+    // plausibly be a reboot.
+    function reconnect() {
+      if (firstFailureMs === null) return; // we were never down
+      banner.hidden = false;
+      banner.textContent = 'Device back online — reloading…';
       if (tickerId !== null) {
         clearInterval(tickerId);
         tickerId = null;
       }
+      window.location.reload();
     }
 
     document.addEventListener('htmx:configRequest', function (evt) {
@@ -93,12 +104,9 @@
       if (!evt.detail) return;
       var xhr = evt.detail.xhr;
       var status = xhr ? xhr.status : 0;
-      // Any HTTP response < 500 means the server is reachable — hide.
-      // (Pre-fix the banner stuck on after the next poll returned 404
-      // because the old check used `successful`, which is true only for
-      // 2xx.)  status === 0 = no response, leave the banner alone;
-      // sendError / timeout handles it.
-      if (status > 0 && status < 500) hide();
+      // Any HTTP response < 500 means the server is reachable again.
+      // status === 0 = no response; leave it to sendError / timeout.
+      if (status > 0 && status < 500) reconnect();
     });
   }