allow --port=8000 to apply as override

[AlbertDeFusco]

I found out that when --port=8000 was explicitly provided on the CLI it would not override the mcp-compose.toml configuration but any other value would.

This PR helps declare that when no --port flag is passed the mcp-compose.toml is used otherwise set the port to 8000. But when --port is passed it has the highest priority.

Here's an example of the case today with version 0.1.11

no port override

❯ mcp-compose serve -c examples/proxy-streamable-http/mcp_compose.toml
...
======================================================================
📡 MCP Server Mode: STREAMABLE-HTTP
======================================================================
  MCP Endpoint:  http://localhost:8888/mcp
  Tools List:    http://localhost:8888/tools
  REST API:      http://localhost:8888/api/v1
  Health Check:  http://localhost:8888/api/v1/health
  Web UI:        http://localhost:9456/ui

with port=8000 override

the mcp endpoint is still on 8888

❯ mcp-compose serve -c examples/proxy-streamable-http/mcp_compose.toml --port 8000
======================================================================
📡 MCP Server Mode: STREAMABLE-HTTP
======================================================================
  MCP Endpoint:  http://localhost:8888/mcp
  Tools List:    http://localhost:8888/tools
  REST API:      http://localhost:8888/api/v1
  Health Check:  http://localhost:8888/api/v1/health
  Web UI:        http://localhost:9456/ui

[echarles]

strange, relauched the test for python 3.11 on ubuntu and failing twice with the same error

https://github.com/datalayer/mcp-compose/actions/runs/25073240867/job/73466337908?pr=33