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/api.ts

@@ -0,0 +1,33 @@
+/**
+ * API utilities for session management and authentication
+ */
+
+let sessionExpiredHandled = false;
+
+/**
+ * Handle session expiration by redirecting to login
+ */
+export function handleSessionExpired(): void {
+  if (sessionExpiredHandled) return;
+  sessionExpiredHandled = true;
+
+  // If we're in the browser, redirect to login
+  if (typeof window !== 'undefined') {
+    window.location.href = '/login?expired=true';
+  }
+}
+
+/**
+ * Check if a session expiration is already being handled
+ * (prevents multiple simultaneous redirects)
+ */
+export function isSessionExpiring(): boolean {
+  return sessionExpiredHandled;
+}
+
+/**
+ * Reset the session expiration flag (for testing)
+ */
+export function resetSessionExpirationFlag(): void {
+  sessionExpiredHandled = false;
+}