Ptufile

- Also trim leading channels without photons (breaking).
- Add property to identify channels with photons.

- Improve typing.

- Detect point scans in image mode.
- Deprecate Python 3.9, support Python 3.13.

- Fix docstring examples not correctly rendered on GitHub.

- Build wheels with NumPy 2.

- Change definition of PtuFile.frequency (breaking).
- Add option to specify number of bins returned by decode_histogram.
- Add option to return histograms of one period.