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

components/ui/convex-prover.tsx

@@ -0,0 +1,26 @@
+"use client";
+
+import { ReactNode } from "react";
+import { ConvexReactClient } from "convex/react";
+import { ConvexBetterAuthProvider } from "@convex-dev/better-auth/react";
+import { authClient } from "@/lib/auth-client";
+
+const convex = new ConvexReactClient(process.env.NEXT_PUBLIC_CONVEX_URL!);
+
+export function ConvexClientProvider({
+  children,
+  initialToken,
+}: {
+  children: ReactNode;
+  initialToken?: string | null;
+}) {
+  return (
+    <ConvexBetterAuthProvider
+      client={convex}
+      authClient={authClient}
+      initialToken={initialToken}
+    >
+      {children}
+    </ConvexBetterAuthProvider>
+  );
+}