[ENH] Add get_server_health MCP tool for server diagnostics and resource monitoring

[Vaishnav88sk]

…rce monitoring

Reference Issues/PRs

Closes #377

What does this implement/fix? Explain your changes.

• Adds src/sktime_mcp/tools/health.py - new tool module with get_server_health_tool()
• Registers the tool in server.py
• Updates tools/init.py exports
• Adds unit tests in tests/test_health.py

Does your contribution introduce a new dependency? If yes, which one?

What should a reviewer concentrate their feedback on?

Any other comments?

PR checklist

For all contributions

• I've added myself to the list of contributors.
• Optionally, I've updated sktime's CODEOWNERS to receive notifications about future changes to these files.
• I've added unit tests and made sure they pass locally.

For new estimators

• I've added the estimator to the online documentation.
• I've updated the existing example notebooks or provided a new one to showcase how my estimator works.

[Vaishnav88sk]

@Shashankss1205