Describe Your Changes

This pull request includes several changes to the RunServer function in the engine/main.cc file, focusing on improving signal handling, API key validation, and CORS handling.

Signal handling improvements:

• Removed an extra semicolon in the signal handler for better code clarity.

API key validation and CORS handling:

• Refactored the API key validation logic to be part of a new pre-routing advice, which now also handles OPTIONS preflight requests for CORS.
• Consolidated and simplified the CORS handling into a single function handle_cors, which is used in both pre-routing and post-handling advices. [1] [2]

Fixes Issues

• bug: cortex blocks preflighted request #2176

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed