feat: add mindmap components from jarvis frontend

- Copied mindmap visualization components (ReactFlow-based interactive graph)
- Added MindmapViewer, ReactFlowEditor, MermaidViewer
- Included all node types: Concept, Task, Idea, Project
- Added controls: NodeCreateModal, ExportButton
- Created mindmap route at /mindmap
- Added useGraphData hook for knowledge graph API
- Copied auth-client and api utilities (dependencies)

Note: Requires better-auth packages to be installed for full compilation

apps/web/src/lib/auth-client.ts

@@ -0,0 +1,106 @@
+/**
+ * BetterAuth client for frontend authentication.
+ *
+ * This client handles:
+ * - Sign in/out operations
+ * - Session management
+ * - Automatic token refresh
+ */
+import { createAuthClient } from "better-auth/react";
+import { credentialsClient } from "better-auth-credentials-plugin/client";
+
+/**
+ * Auth client instance configured for Jarvis.
+ */
+export const authClient = createAuthClient({
+  // Base URL for auth API
+  baseURL: typeof window !== "undefined"
+    ? window.location.origin
+    : process.env.BETTER_AUTH_URL || "http://localhost:3042",
+
+  // Plugins
+  plugins: [
+    // Credentials client for username/password auth
+    credentialsClient(),
+  ],
+});
+
+/**
+ * Export commonly used auth functions.
+ */
+export const {
+  signIn,
+  signOut,
+  useSession,
+  getSession,
+} = authClient;
+
+/**
+ * Sign in with username and password.
+ * Returns the session on success, throws on failure.
+ *
+ * Uses direct fetch since our server accepts username (not email)
+ * and the default BetterAuth client expects email.
+ */
+export async function signInWithCredentials(username: string, password: string) {
+  const baseURL = typeof window !== "undefined"
+    ? window.location.origin
+    : process.env.BETTER_AUTH_URL || "http://localhost:3042";
+
+  const response = await fetch(`${baseURL}/api/auth/sign-in/credentials`, {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/json",
+    },
+    credentials: "include", // Include cookies
+    body: JSON.stringify({ username, password }),
+  });
+
+  if (!response.ok) {
+    const error = await response.json().catch(() => ({}));
+    throw new Error(error.message || "Authentication failed");
+  }
+
+  const data = await response.json();
+  return data;
+}
+
+/**
+ * Get the current access token for API calls.
+ * Returns null if not authenticated.
+ */
+export async function getAccessToken(): Promise<string | null> {
+  const session = await getSession();
+  if (!session?.data?.user) {
+    return null;
+  }
+
+  // Type assertion for custom user fields
+  const user = session.data.user as {
+    accessToken?: string;
+    tokenExpiresAt?: number;
+  };
+
+  // Check if token is expired (with 1 minute buffer)
+  if (user.tokenExpiresAt && user.tokenExpiresAt - Date.now() < 60000) {
+    // Token is expired or about to expire
+    // The session will be refreshed automatically by BetterAuth
+    // but we should return null to trigger a re-auth if needed
+    return null;
+  }
+
+  return user.accessToken || null;
+}
+
+/**
+ * Check if the current user is an admin.
+ */
+export async function isAdmin(): Promise<boolean> {
+  const session = await getSession();
+  if (!session?.data?.user) {
+    return false;
+  }
+
+  const user = session.data.user as { isAdmin?: boolean };
+  return user.isAdmin === true;
+}