feat(frontend): micro-interactions — page-enter transition + MetricTile lift

- Add animate-fade-up utility (reduced-motion aware) and a PageTransition
  wrapper; every dashboard view now rises + settles on mount/route change.
- MetricTile gains a subtle hover lift (-translate-y) + ring-focus glow.
- Theme toggle and command palette (⌘K) already existed and persist; no-op.

services/frontend/src/components/shared/index.ts

@@ -1,5 +1,6 @@
 export { GuildChannelPicker } from "./guild-picker";
 export { MarkdownLite } from "./markdown";
+export { PageTransition } from "./page-transition";
 export { MetricTile, SectionHeader } from "./section";
 export {
   EmptyState,