Convex MCP server

# Convex HTTP actions Demonstrates defining custom HTTP actions that talk to Convex (e.g. to hook up to a webhook). ``` curl -v 'http://127.0.0.1:8001/getMessagesByAuthor?authorNumber=123' curl -v -d '{ "author": "User 123", "body": "Hello world" }' \ -H 'content-type: application/json' 'http://127.0.0.1:8001/postMessage' ```