Log warning (or throw error?) when a user binds an http transport multiple times to the same server

[brettimus]

There is an easy way to shoot oneself in the foot with mcp-lite: If you repeatedly instantiate the streamable http transport and bind it to the same server multiple times, you can end up breaking a stateful server. The reason for this is that the transport overrides methods in the server to which it is bound for sending notifications and sending requests back to the client.

I think for now we should log a warning when someone does this, or perhaps have a "strict" flag that throws an error?