feat(slice-3): design-system foundation — Wiggleverse tokens, fonts, brand marks, UI kit (per ui/designs export)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/styles/index.css

@@ -0,0 +1,7 @@
+/* Global style entry point — Wiggleverse design-system tokens (copied from the
+   ui/designs export) + the ecomm app chrome built on them. */
+@import "./fonts.css";
+@import "./tokens-colors.css";
+@import "./tokens-typography.css";
+@import "./tokens-spacing.css";
+@import "./app.css";