Add admin buttons to delete and resubmit samples

[lkeegan]

• add DELETE admin/samples/<sample_id> API endpoint
  • deletes the sample and all associated input files and results
• add delete button to admin interface with modal confirmation dialog
  • resolves Admin delete samples #39
• add POST admin/resubmit-sample/<sample_id> API endpoint
  • deletes any existing results for the sample, then sets its status to QUEUED
• add resubmit button to admin interface with modal confirmation dialog
  • resolves Admin resubmit sample #40

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.84848% with 5 lines in your changes missing coverage. Please review.

Project coverage is 78.82%. Comparing base (4fb00da) to head (d8b9477).

Files with missing lines	Patch %	Lines
backend/src/predicTCR_server/app.py	82.75%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #45      +/-   ##
==========================================
+ Coverage   78.18%   78.82%   +0.63%     
==========================================
  Files           8        8              
  Lines         651      680      +29     
==========================================
+ Hits          509      536      +27     
- Misses        142      144       +2     

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