fix(migrations): clean the alembic migrations & scratch revisions

[frgfm]

This PR introduces the following modifications:

• scratch previous migrations
• clean setup so that revision are properly generated
• update docker to run migration properly before starting

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 83.86%. Comparing base (c7fea64) to head (9f04edf).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/app/db.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
- Coverage   83.95%   83.86%   -0.10%     
==========================================
  Files          29       29              
  Lines         916      917       +1     
==========================================
  Hits          769      769              
- Misses        147      148       +1     

Flag	Coverage Δ
unittests	83.86% <66.66%> (-0.10%)	⬇️

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