Implement database administration

Add routes and admin panel elements for creating a database backup,
restoring from a backup, deleting the existing schedule, and replacing
the database with the demo schedule.  These server as crude ways to
manage the data stored in the system.

server/api/admin/database-export.post.ts

@@ -0,0 +1,15 @@
+import { readNextSessionId, readNextUserId, readSchedule, readSessions, readSubscriptions, readUsers } from "~/server/database";
+
+export default defineEventHandler(async (event) => {
+	await requireServerSessionWithAdmin(event);
+	setHeader(event, "Content-Disposition", 'attachment; filename="database-dump.json"');
+	setHeader(event, "Content-Type", "application/json; charset=utf-8");
+	return {
+		nextUserId: await readNextUserId(),
+		users: await readUsers(),
+		nextSessionId: await readNextSessionId(),
+		sessions: await readSessions(),
+		subscriptions: await readSubscriptions(),
+		schedule: await readSchedule(),
+	};
+})