feat(frontend): Vue 3 workspace UI with light/dark mode

- Vue 3 + Vite + Pinia + Vue Router, Axios client with JWT interceptor
- Auth views (login/register), dashboard with workspace switcher and search
- Nested PageTree sidebar, TipTap rich-text editor with debounced save
- Live collaboration via Socket.IO (remote updates, presence avatars, typing)
- Comments thread per page, invite-members card, member list
- Theme store (light/dark/system) persisted, CSS variables, ThemeToggle
- Multi-stage Dockerfile (build + nginx) for hosting

frontend/package.json

@@ -0,0 +1,26 @@
+{
+  "name": "openstack-frontend",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "@tiptap/core": "^2.4.0",
+    "@tiptap/pm": "^2.4.0",
+    "@tiptap/starter-kit": "^2.4.0",
+    "@tiptap/vue-3": "^2.4.0",
+    "axios": "^1.7.2",
+    "pinia": "^2.1.7",
+    "socket.io-client": "^4.7.5",
+    "vue": "^3.4.0",
+    "vue-router": "^4.3.0"
+  },
+  "devDependencies": {
+    "@vitejs/plugin-vue": "^5.0.0",
+    "vite": "^5.0.0"
+  }
+}