fix: shrink navbar brand on mobile so navbar controls fit one row

The selector was already narrow enough — the real culprit was the
.navbar-brand.h1 sitting at Bootstrap's default 2.5rem (40px), which
on a Samsung S20 ate ~200px just for 'mc-webui'. Cap brand at
1.25rem on screens ≤ 768px so the bell + selector + menu can sit
beside it on one row.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/static/css/style.css

@@ -557,6 +557,11 @@ main {
         gap: 0.25rem !important;
     }
 
+    /* Navbar: Shrink brand title so all controls fit on one row */
+    .navbar-brand.h1 {
+        font-size: 1.25rem;
+    }
+
     /* Navbar: Channel selector on mobile */
     #channelSelectorInput {
         min-width: 0 !important;