Fix header-right button group alignment on mobile

Add justify-content: flex-end to .header-right on mobile so
buttons align to the right edge instead of starting from left.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jeremymanning

index.html

@@ -743,7 +743,7 @@
             .logo { font-size: 0.95rem; }
             .header-left { gap: 0.3rem; flex: 0 0 auto; }
             .header-actions { gap: 0.25rem; flex: 1; min-width: 0; }
-            .header-right { gap: 0.25rem; flex: 1; min-width: 0; }
+            .header-right { gap: 0.25rem; flex: 1; min-width: 0; justify-content: flex-end; }
             .btn-icon, .control-btn { min-width: 34px; min-height: 34px; font-size: 0.85rem; }
             /* Make dropdown arrow easier to see on mobile */
             .custom-select-arrow { font-size: 0.9rem; }