Add files via upload

frontend/src/store/useUIStore.js

@@ -0,0 +1,13 @@
+import { create } from 'zustand'
+
+const useUIStore = create((set) => ({
+  sidebarOpen:   true,
+  sidebarTab:    'projects',   // 'projects' | 'agenda'
+  showHeatmap:   false,
+
+  toggleSidebar:  ()    => set(s => ({ sidebarOpen: !s.sidebarOpen })),
+  setSidebarTab:  (tab) => set({ sidebarTab: tab }),
+  toggleHeatmap:  ()    => set(s => ({ showHeatmap: !s.showHeatmap })),
+}))
+
+export default useUIStore