Potential fix for code scanning alert no. 21: Missing rate limiting

[LightZirconite]

Potential fix for https://github.com/LightZirconite/Microsoft-Rewards-Bot/security/code-scanning/21

The best way to address this issue is to apply rate limiting to the handler for '/' (the dashboard UI route). The recommended approach is to use the well-known express-rate-limit middleware package, which is specifically designed for Express applications and is safe and highly maintained. We should import and instantiate this middleware (with sensible defaults, e.g., 100 requests per 15 minutes from a single IP), and apply it to the '/' route. This can be done by creating a limiter instance before routes are setup, and then attaching it as middleware specifically to that route:

• In src/dashboard/server.ts, import express-rate-limit.
• In the DashboardServer class, instantiate a limiter with reasonable defaults.
• Attach the limiter to the '/' route, i.e., in setupRoutes, before the route handler for '/' (this.app.get('/', [limiter], handler);).

If express-rate-limit is not yet installed, the dependency must be added to the project.

---

Suggested fixes powered by Copilot Autofix. Review carefully before merging.