feat(frontend): mobile bottom nav, chatbot overhaul, responsive polish

- MobileNav: safe-area-aware bottom tab bar (< md), mirrors desktop nav
- Chatbot: timestamps, per-message copy, retry-on-fail, auto-grow composer,
  MarkdownLite (XSS-safe React nodes, no dangerouslySetInnerHTML)
- AppFrame: NavRail (md+) + MobileNav (< md) + bottom content padding
- Design system: SignalTone ambient (signal/amber/vermilion) driving WebGL
  haze + topbar status pill; SectionHeader/MetricTile; globals.css tokens
- Views: dashboard hero + AmbientField, analysis/media responsive grids

services/frontend/src/app/(dashboard)/media/view.tsx

@@ -85,7 +85,7 @@ export function MediaView({ initialStatus }: { initialStatus?: MediaState }) {
 
           <div className="min-w-0 flex-1">
             <div className="eyebrow mb-1">Now playing</div>
-            <h2 className="display truncate text-2xl text-ink">
+            <h2 className="display text-balance text-2xl text-ink">
               {current?.title ?? "Nothing queued"}
             </h2>
             {current?.source && (