fix(ui): actionable toasts linger, and a dead hotkey shows in the sidebar

Every toast auto-dismissed after 2.8 s — fine for a success receipt, too
short to read AND act on an error. Errors and warnings now stay 10 s and can
be clicked away; success is unchanged.

The hotkey-conflict warning also needed a trace outside the toast: the ⚠ in
Settings only helps someone who opens the panel. A dot on the sidebar Settings
entry (plus a tooltip) is now the cue in the main UI that a combo is dead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/app.autofill.js

@@ -36,6 +36,17 @@ function renderHotkeyConflicts() {
                                'the hotkey does nothing. Pick another one.';
         else       btn.removeAttribute('title');
     }
+    // Dot on the Settings button: the ⚠ inside the panel only helps someone who
+    // opens it, and the toast may well have been missed. This is the only cue
+    // left in the main UI that a hotkey is silently dead.
+    const gear = document.getElementById('settingsBtn');
+    if (gear) {
+        gear.classList.toggle('has-alert', bad.size > 0);
+        if (bad.size > 0)
+            gear.title = 'A hotkey combo is already used by another app — see Autofill settings';
+        else if (gear.title.startsWith('A hotkey combo'))
+            gear.title = 'Settings';
+    }
 }
 
 // Format a combo for human display: "Ctrl+Shift+L".