feat: add HTTP streaming support

[hwittenborn]

This adds support for running the MCP server via an HTTP endpoint. The implementation for this was largely taken from the MCP library's documentation.

[Tiberriver256]

Thanks for opening this @hwittenborn. I've been... mulling on it lol. Still not sure if I want to merge it in or not but figured I would at least break the silence.

Was a little hesitant for two reasons:

• Security Implications - Running remote is different from local so... just a lot to think through there. Kinda wanted to refactor into fast-mcp or some framework that handles the protocol and all the stuff around it (auth/etc.) for me so if security stuff comes I can just patch but.. also wasn't feeling up to a larger refactor.
• Microsoft launching their own - See the announcement

I was kind of hoping they would launch with SSE right out of the box but it seems they followed suit with me and launched just supporting stdio.