Initial commit: Agile Project Manager

- Complete React + TypeScript application with Vite
- Dashboard with charts and metrics visualization
- Kanban board with drag-and-drop functionality
- Product backlog management with user stories
- Sprint planning and tracking features
- Comprehensive UI component library (shadcn/ui)
- Tailwind CSS styling with dark mode support
- Context-based state management
- Mock data for immediate testing and demonstration

components/ui/use-mobile.ts

@@ -0,0 +1,21 @@
+import * as React from "react";
+
+const MOBILE_BREAKPOINT = 768;
+
+export function useIsMobile() {
+  const [isMobile, setIsMobile] = React.useState<boolean | undefined>(
+    undefined,
+  );
+
+  React.useEffect(() => {
+    const mql = window.matchMedia(`(max-width: ${MOBILE_BREAKPOINT - 1}px)`);
+    const onChange = () => {
+      setIsMobile(window.innerWidth < MOBILE_BREAKPOINT);
+    };
+    mql.addEventListener("change", onChange);
+    setIsMobile(window.innerWidth < MOBILE_BREAKPOINT);
+    return () => mql.removeEventListener("change", onChange);
+  }, []);
+
+  return !!isMobile;
+}