Add cdn timeout handling

[lukechatton]

Summary

• classify bundle download failures to produce user-friendly errors for timeout and unreachable CDN cases
• detect timeout-like failures (including Curl error 28) and include the CDN host in the message shown to users
• update both client bundle load and main menu package download flows to display the friendly error directly

Problem

When the game CDN times out or cannot be reached, users see a generic error that does not explain what to do.

Result

Users now get actionable guidance such as checking connection/firewall/VPN and retrying, specifically for CDN timeout/connectivity failures.

Testing

• not run (code-path change only; no Unity runtime verification in this environment)