feat: dashboard, Convex auth, UI components, and LemonSpace branding

- Add dashboard shell with auth integration
- Wire Better Auth / Convex (client, server, HTTP routes)
- Add shadcn-style UI primitives and logo assets
- Update global styles and landing page
- Add internal docs (.docs)

Made-with: Cursor

package.json

@@ -9,8 +9,11 @@
     "lint": "eslint"
   },
   "dependencies": {
+    "@convex-dev/better-auth": "^0.11.3",
+    "better-auth": "^1.5.6",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "convex": "^1.34.0",
     "lucide-react": "^1.6.0",
     "next": "16.2.1",
     "radix-ui": "^1.4.3",
@@ -18,7 +21,8 @@
     "react-dom": "19.2.4",
     "shadcn": "^4.1.0",
     "tailwind-merge": "^3.5.0",
-    "tw-animate-css": "^1.4.0"
+    "tw-animate-css": "^1.4.0",
+    "zod": "^4.3.6"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",