Fix/gh 48 export relative paths

[mbsantiago]

This pull request addresses the issue raised by @namitha-sh in #48, where exporting datasets includes full recording paths. This behavior hinders dataset sharing, as paths often need modification for re-import into Whombat. Furthermore, full paths can contain sensitive information that should not be shared.

This PR implements the following changes to export recordings with paths relative to the dataset's audio_dir:

1. Unit Test: Added a unit test to verify that dataset import and export correctly handle relative paths. The test imports and exports the test dataset, then checks if the exported recording paths are relative to the audio_dir.

2. Dataset API Enhancements: Created import_dataset and export_dataset methods within the whombat.api.datasets module. These methods encapsulate the logic for dataset import and export operations. Currently, AOEF format is supported, with plans to add support for other formats in the future.

3. REST API Integration: Updated the import and export REST API routes to utilize the new dataset API methods.

4. Path Modification: Modified the export functions to remove the audio_dir prefix from recording paths, ensuring they are relative.

All tests are currently passing.

[codecov]

Codecov Report

Attention: Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.

Project coverage is 66.60%. Comparing base (dd70269) to head (b50408f).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
back/src/whombat/routes/datasets.py	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #49      +/-   ##
==========================================
+ Coverage   66.47%   66.60%   +0.12%     
==========================================
  Files         179      179              
  Lines        8367     8372       +5     
==========================================
+ Hits         5562     5576      +14     
+ Misses       2805     2796       -9     

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