v0.6.1 — fix: pskt --version stale after install

Patch release. Fixes a cosmetic bug where pskt --version reported the previous version after a fresh install.

What changed

__version__ was hardcoded in src/perskent/__init__.py and was forgotten on the v0.6.0 bump, so a fresh install of 0.6.0 printed:

```
$ pskt --version
perskent 0.5.0
```

even though pipx had correctly installed the 0.6.0 wheel. The fix reads the version from the installed package metadata via `importlib.metadata.version("perskent")`, so __version__ always tracks `pyproject.toml` and this can't happen again.

No behavior changes — only the version string.

Installation

```bash
curl -fsSL https://raw.githubusercontent.com/Alecell/Perskent/main/install.sh | sh
```

Or upgrade:

```bash
pipx upgrade perskent
```