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/components/shared/index.ts

@@ -1,3 +1,4 @@
 export { GuildChannelPicker } from "./guild-picker";
+export { MarkdownLite } from "./markdown";
 export { MetricTile, SectionHeader } from "./section";
 export { EmptyState, ErrorState, LoadingState } from "./states";