feat: migrate frontend to Astro SSG with design system

- Replace monolithic React SPA (App.tsx) with 7 Astro pages (+ routing)
- Implement full design system from design/ (OKLCH tokens, Tailwind 4 @theme)
- Add 12 Astro components (Button, Badge, Card, Sidebar, Header, states)
- Add 11 React islands (AuthGuard, MessageFeed, VoiceControls, AudioVisualizer, etc.)
- Add 3 Zustand stores (UI, voice, message state)
- Add CSS architecture: dark/light themes, glassmorphism, fluid typography, animations
- Add 404, login, settings, recordings pages
- Remove 40+ legacy React SPA files
- Add Particles background and MascotChat deferred islands
- Wire WebSocket bridge for real-time messages and voice events

Build: 7 pages in ~900ms
Typecheck: clean (0 errors)
Lint: clean (0 errors)

services/frontend/src/shared/ui/tabs.tsx

@@ -1,50 +0,0 @@
-import * as TabsPrimitive from "@radix-ui/react-tabs";
-import type * as React from "react";
-import { cn } from "../lib/utils";
-
-export const Tabs = TabsPrimitive.Root;
-
-export function TabsList({
-  className,
-  ...props
-}: React.ComponentPropsWithoutRef<typeof TabsPrimitive.List>) {
-  return (
-    <TabsPrimitive.List
-      className={cn(
-        "inline-flex h-10 items-center justify-center rounded-lg bg-muted p-1 text-muted-foreground",
-        className,
-      )}
-      {...props}
-    />
-  );
-}
-
-export function TabsTrigger({
-  className,
-  ...props
-}: React.ComponentPropsWithoutRef<typeof TabsPrimitive.Trigger>) {
-  return (
-    <TabsPrimitive.Trigger
-      className={cn(
-        "inline-flex items-center justify-center whitespace-nowrap rounded-lg px-3 py-1.5 text-sm font-medium transition-all focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring disabled:pointer-events-none disabled:opacity-50 data-[state=active]:bg-background data-[state=active]:text-foreground data-[state=active]:shadow-sm",
-        className,
-      )}
-      {...props}
-    />
-  );
-}
-
-export function TabsContent({
-  className,
-  ...props
-}: React.ComponentPropsWithoutRef<typeof TabsPrimitive.Content>) {
-  return (
-    <TabsPrimitive.Content
-      className={cn(
-        "mt-6 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
-        className,
-      )}
-      {...props}
-    />
-  );
-}