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/lib/cache.js

@@ -0,0 +1,21 @@
+import { CACHE_TTL_MS } from "./config.js";
+
+const cache = new Map();
+
+export function getCached(key) {
+    const entry = cache.get(key);
+    if (!entry) return null;
+    if (Date.now() > entry.expiresAt) {
+        cache.delete(key);
+        return null;
+    }
+    return entry.value;
+}
+
+export function setCached(key, value, ttlMs = CACHE_TTL_MS) {
+    cache.set(key, { value, expiresAt: Date.now() + ttlMs });
+}
+
+export function clearCached(key) {
+    cache.delete(key);
+}