feat(frontend): skeleton loading states, empty-state glow, light-mode polish

- Add shared skeleton building blocks (SkeletonHero, SkeletonMetricRow,
  SkeletonPanel, SkeletonRows) and wire them into every view's initial
  loading branch, replacing bare spinners for a cohesive shimmering shell.
- Polish EmptyState with a glow-ring icon chip instead of a flat icon.
- Harden .light theme: color-scheme, tuned scrollbar + selection for pale
  canvas. Dark/light theme toggle (next-themes) already persisted in TopBar.

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

@@ -1,4 +1,12 @@
 export { GuildChannelPicker } from "./guild-picker";
 export { MarkdownLite } from "./markdown";
 export { MetricTile, SectionHeader } from "./section";
-export { EmptyState, ErrorState, LoadingState } from "./states";
+export {
+  EmptyState,
+  ErrorState,
+  LoadingState,
+  SkeletonHero,
+  SkeletonMetricRow,
+  SkeletonPanel,
+  SkeletonRows,
+} from "./states";