Remove private DICOM tag for PIXL project name

[p-j-smith]

Description

Fixes #526

• remove the private DICOM tag for the PIXL project name. Instead, pass the project name in the payload to the Orthanc Anon plugin and export API
• simplify pixl_dcmd.main.anonymise_dicom - move the config loading and db updating into separate functions (happy to move into a separate PR if it's confusing things here)
• update tests to reflect changes

Type of change

Please delete options accordingly to the description.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Suggested Checklist

• I have performed a self-review of my own code.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have commented my code, particularly in hard-to-understand areas.
• I have passed on my local host device. (see further details at the CONTRIBUTING document)
• Make sure your branch is up-to-date with main branch. See CONTRIBUTING for a general example to syncronise your branch with the main branch.
• I have requested review to this PR.
• I have addressed and marked as resolved all the review comments in my PR.
• Finally, I have selected squash and merge

[codecov]

Codecov Report

Attention: Patch coverage is 98.27586% with 1 line in your changes missing coverage. Please review.

Project coverage is 87.35%. Comparing base (76e35fc) to head (9693cda).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pixl_export/src/pixl_export/main.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #527      +/-   ##
==========================================
+ Coverage   87.30%   87.35%   +0.05%     
==========================================
  Files          76       76              
  Lines        3442     3378      -64     
==========================================
- Hits         3005     2951      -54     
+ Misses        437      427      -10     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[stefpiatek]

Nice, this makes life a lot easier 🎉