fix: add --version/-V flag to CLI (#312)

The CLI previously crashed when running `ha-mcp --version` because it
would attempt to create the server, which requires HOMEASSISTANT_URL
and HOMEASSISTANT_TOKEN environment variables.

Now the --version and -V flags are handled early, before any server
initialization, allowing users to check their installed version without
configuration.

Fixes #290

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: julienld