feat: implement user authentication and license management system

- Added schema for users, licenses, and license hostnames in the database.
- Created storage utility for reading and writing JSON files.
- Developed user service for user registration, authentication, and retrieval.
- Implemented authentication middleware to protect routes.
- Built LicenseCard component to display license details.
- Created SiteNav component for navigation with user authentication status.
- Established AuthContext for managing authentication state and actions.
- Developed Home page to display available plugins.
- Created LicenseManager page for managing licenses with forms for creation and verification.
- Implemented PluginDetail page to show detailed information about a specific plugin.
- Added utility functions for date formatting.

server/middleware/auth.js

@@ -0,0 +1,23 @@
+import jwt from "jsonwebtoken";
+import { JWT_SECRET } from "../lib/config.js";
+import { getUserById } from "../lib/userService.js";
+
+export async function requireAuth(req, res, next) {
+    const authHeader = req.headers.authorization || "";
+    const token = authHeader.startsWith("Bearer ") ? authHeader.slice(7).trim() : null;
+    if (!token) {
+        return res.status(401).json({ error: "Inloggen vereist." });
+    }
+    try {
+        const payload = jwt.verify(token, JWT_SECRET);
+        const user = await getUserById(payload.sub);
+        if (!user) {
+            return res.status(401).json({ error: "Gebruiker niet gevonden." });
+        }
+        req.user = user;
+        req.token = token;
+        next();
+    } catch (error) {
+        return res.status(401).json({ error: "Ongeldige of verlopen token." });
+    }
+}