chore: Cleanup of ethereum Django app

[gzurowski]

• Remove unused utility functions.
• Relocate the only used utility into the lib package.
• Remove unused migrations folder.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.

Project coverage is 67.54%. Comparing base (6f325f6) to head (0f73ce7).

Files with missing lines	Patch %	Lines
src/ethereum/lib.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2126      +/-   ##
==========================================
+ Coverage   67.51%   67.54%   +0.02%     
==========================================
  Files         434      433       -1     
  Lines       24199    24178      -21     
==========================================
- Hits        16339    16331       -8     
+ Misses       7860     7847      -13     

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