feat(proxy): add optional auth for dashboard and API

Co-Authored-By: Claude <noreply@anthropic.com>

packages/proxy/src/auth/sessionStore.ts

@@ -0,0 +1,22 @@
+import { randomUUID } from 'node:crypto';
+
+interface Session {
+  username: string;
+  createdAt: number;
+}
+
+const sessions = new Map<string, Session>();
+
+export function createSession(username: string): string {
+  const token = randomUUID();
+  sessions.set(token, { username, createdAt: Date.now() });
+  return token;
+}
+
+export function validateSession(token: string): Session | null {
+  return sessions.get(token) ?? null;
+}
+
+export function removeSession(token: string): void {
+  sessions.delete(token);
+}