Add hot reload functionality to SSE

[TheRobotCarlson]

Motivation and Context

I use Cursor to build and test my MCP servers and often it updates the servers, but can't restart them once the code has been edited.

This adds the hot reload option to the FastMCP settings and uses it in the SSE uvicorn config.

How Has This Been Tested?

Locally

Breaking Changes

No

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[Kludex]

Did you test this PR? I don't think this will reload, given the app is passed as an ASGI application object. It only works when it's passed as string.

[TheRobotCarlson]

@Kludex I had monkey-patched that in my tests. I'll close out this PR until I can come back to address that.

[Edison-A-N]

Consider trying this: https://gist.github.com/Edison-A-N/f4fa399c456525f5d821aa0ff9932ee2