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)

pnpm-lock.yaml

@@ -267,6 +267,9 @@ importers:
       tailwind-merge:
         specifier: ^3.6.0
         version: 3.6.0
+      zustand:
+        specifier: ^5.0.14
+        version: 5.0.14(@types/react@19.2.14)(react@19.2.6)
     devDependencies:
       '@biomejs/biome':
         specifier: latest
@@ -6047,6 +6050,24 @@ packages:
   zod@4.4.3:
     resolution: {integrity: sha512-ytENFjIJFl2UwYglde2jchW2Hwm4GJFLDiSXWdTrJQBIN9Fcyp7n4DhxJEiWNAJMV1/BqWfW/kkg71UDcHJyTQ==}
 
+  zustand@5.0.14:
+    resolution: {integrity: sha512-/8tAspM5LMPr28b3fwLYrtdj77ECpfZviaP75CMTnwO8ISyaE4GDIG/9rDDYq/cH9D2Xw2A2RXglLInmVBQB/g==}
+    engines: {node: '>=12.20.0'}
+    peerDependencies:
+      '@types/react': '>=18.0.0'
+      immer: '>=9.0.6'
+      react: '>=18.0.0'
+      use-sync-external-store: '>=1.2.0'
+    peerDependenciesMeta:
+      '@types/react':
+        optional: true
+      immer:
+        optional: true
+      react:
+        optional: true
+      use-sync-external-store:
+        optional: true
+
   zwitch@2.0.4:
     resolution: {integrity: sha512-bXE4cR/kVZhKZX/RjPEflHaKVhUVl85noU3v6b8apfQEc1x4A+zBxjZ4lN8LqGd6WZ3dl98pY4o717VFmoPp+A==}
 
@@ -11514,4 +11535,9 @@ snapshots:
 
   zod@4.4.3: {}
 
+  zustand@5.0.14(@types/react@19.2.14)(react@19.2.6):
+    optionalDependencies:
+      '@types/react': 19.2.14
+      react: 19.2.6
+
   zwitch@2.0.4: {}