Feature/support custom rotations csv

[javlor]

Add CSV import for custom tracker rotation schedules. This PR adds the solarfarmer.custom_rotations module, which lets users convert a CSV file of tracker rotation angles into the protobuf format consumed by the SolarFarmer API. It depends on feature/support-custom-tracker-workflow.

• New module (custom_rotations.py) with utils from_csv, offset_from_utc, csv_to_protobuf, validation_tracker_rotation_ids, check_weather_covers_rotation_period, check_compatible_time_resolutions. This performs a number of checks and validation for the tracker data from the expected CSV file(s) of tracker rotation angles.
• New method TrackersConditionsDataset.to_protobuf_file updated to produce the protobuf files expected by SolarFarmer API.
• New tests (test_custom_rotations.py)
• Documentation updates: a new page custom-tracker-rotations.md describes the CSV format, sign convention, validation helpers, and the multi-file output behavior. The API reference page is updated with autodoc entries for all public symbols.