fix(server): handle exceptions in messages route

[GinWU05]

This PR includes two small but important fixes to improve the overall usability and robustness of the claude-code-router.

Changes:

1. Corrected Outdated Command in Status Message (src/utils/status.ts)

   • The status message displayed by ccr status was suggesting the outdated command ccr close.
   • This has been updated to the correct command, ccr stop, to avoid user confusion and align with the current CLI implementation.

2. Added Exception Handling for /v1/messages Route (src/index.ts)

   • Previously, if a downstream API call (e.g., to OpenAI/DeepSeek) failed, the server would catch the exception but not send a response to the client. This caused the client's request to hang until it timed out.
   • An error handling mechanism has been added to the catch block. Now, if an error occurs, the server will immediately respond with a 500 Internal Server Error status and a JSON body containing the error details. This ensures the client receives a prompt and clear response upon failure.

These changes enhance the user experience and make the server's behavior more predictable and reliable.

Thank you for your review and consideration!