add flag for interpolation

[sahiljhawar]

This PR closes #21

[Copilot]

Pull Request Overview

This PR adds a new boolean interpolation parameter to control spline interpolation for short gaps in historical solar wind data. Previously, interpolation was always applied when historical data was available, but now it can be optionally disabled.

Key changes:

• Added interpolation parameter with default False to control interpolation behavior
• Updated function signatures and parameter passing throughout the call chain
• Modified interpolation flag setting to be conditional based on the parameter

Reviewed Changes

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

File	Description
swvo/io/solar_wind/read_solar_wind_from_multiple_models.py	Added interpolation parameter to main function and helper functions, made interpolation conditional
tests/io/solar_wind/test_read_solar_wind_from_multiple_models.py	Updated test calls to explicitly set interpolation=True

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