Have the refresh button check for a new build too

The version poller already diffs /api/version against the manifest
captured at boot -- hot-swapping changed CSS, reloading for changed
JS/HTML once playback allows -- but only on its own 60s tick or when the
tab regains visibility. Pressing refresh now runs that same check in the
background, so a tab left open across a deploy picks the new build up
when the user asks for fresh content rather than up to a minute later.
App.version.checkNow() exposes it; with no baseline (the endpoint was
down at boot) it just adopts the current manifest, since there is nothing
to compare against yet.

Verified against the running app: appending to style.css and pressing
refresh swapped the tag to style.css?v=<hash> with the page still alive,
and appending to a .js file reloaded the page.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QBDkEXP4htyXTCZUwMLphd

frontend/js/ui.js

@@ -461,6 +461,13 @@ App.ui = App.ui || {};
 
         if (reloadChannelBtn) {
             reloadChannelBtn.onclick = () => {
+                // Refresh means "give me the current everything": the videos
+                // below, and the app itself. The version check runs in the
+                // background and only acts if the deployed assets actually
+                // differ from what this tab is running.
+                if (App.version && typeof App.version.checkNow === 'function') {
+                    App.version.checkNow();
+                }
                 App.videos.resetAndReload();
             };
         }