feat: implement user authentication and admin management

- Add user management API endpoints for listing and creating users.
- Implement login and logout functionality with rate limiting.
- Create UI components for login form, logout button, and animated elements.
- Add session management with JWT and secure cookie handling.
- Seed initial admin user if no users exist.
- Introduce utility functions for password hashing and user authentication.
- Set up proxy middleware for route protection and security headers.
- Create a JSON file for user data storage.
- Add links configuration for external resources.

frontend/app/components/CountUp.tsx

@@ -0,0 +1,82 @@
+"use client";
+
+import { useEffect, useRef, useState } from "react";
+
+interface CountUpProps {
+  /** Target number to count up to */
+  to: number;
+  /** String appended after the number (e.g. "%", " MB", "+") */
+  suffix?: string;
+  /** String prepended before the number */
+  prefix?: string;
+  /** Animation duration in ms */
+  duration?: number;
+  /** Decimal places to show */
+  decimals?: number;
+}
+
+export default function CountUp({
+  to,
+  suffix = "",
+  prefix = "",
+  duration = 1800,
+  decimals = 0,
+}: CountUpProps) {
+  const ref = useRef<HTMLSpanElement>(null);
+  const [current, setCurrent] = useState(0);
+  const [started, setStarted] = useState(false);
+
+  useEffect(() => {
+    const el = ref.current;
+    if (!el) return;
+
+    const observer = new IntersectionObserver(
+      ([entry]) => {
+        if (entry.isIntersecting && !started) {
+          setStarted(true);
+          observer.disconnect();
+        }
+      },
+      { threshold: 0.5 },
+    );
+
+    observer.observe(el);
+    return () => observer.disconnect();
+  }, [started]);
+
+  useEffect(() => {
+    if (!started) return;
+
+    // Skip animation if user prefers reduced motion
+    if (window.matchMedia("(prefers-reduced-motion: reduce)").matches) {
+      setCurrent(to);
+      return;
+    }
+
+    const startTime = performance.now();
+    let raf: number;
+
+    function tick(now: number) {
+      const elapsed = now - startTime;
+      const progress = Math.min(elapsed / duration, 1);
+      // Ease-out quart — fast start, smooth finish
+      const eased = 1 - Math.pow(1 - progress, 4);
+      setCurrent(eased * to);
+      if (progress < 1) raf = requestAnimationFrame(tick);
+    }
+
+    raf = requestAnimationFrame(tick);
+    return () => cancelAnimationFrame(raf);
+  }, [started, to, duration]);
+
+  const display =
+    decimals > 0 ? current.toFixed(decimals) : Math.floor(current).toString();
+
+  return (
+    <span ref={ref}>
+      {prefix}
+      {display}
+      {suffix}
+    </span>
+  );
+}