Add hostname to output

[JannikSt]

Summary

• Adds hostname to the UI title bar: ibtop - InfiniBand Monitor @ {hostname}
• Adds hostname field to JSON output for programmatic access
• Adds hostname crate as dependency

Closes #8

Test plan

• Run IBTOP_FAKE_DATA=1 cargo run -- --json and verify hostname appears in JSON output
• Run IBTOP_DEMO=1 cargo run and verify hostname appears in title bar

[Copilot]

Pull request overview

This PR adds hostname information to both the UI title bar and JSON output, making it easier to identify which host is being monitored, especially useful in multi-host environments.

• Adds hostname crate (v0.4) as a dependency
• Wraps JSON output in a new IbtopOutput struct containing hostname and adapters
• Displays hostname in the UI title bar with format: "ibtop - InfiniBand Monitor @ {hostname}"

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Cargo.toml	Bumps version to 0.1.6 and adds hostname = "0.4" dependency
Cargo.lock	Updates lock file with hostname crate and its transitive dependencies (cfg-if, libc, windows-link)
src/types.rs	Introduces IbtopOutput struct to wrap hostname and adapter data for JSON output
src/main.rs	Retrieves hostname in JSON mode and wraps output with new IbtopOutput struct
src/ui.rs	Adds hostname to UI title bar by calling hostname::get() during each frame render

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