Refactor to use only .md files and add tests

[arhimede]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 73.23944% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.64%. Comparing base (8370856) to head (cb103ff).
⚠️ Report is 9 commits behind head on live.

Files with missing lines	Patch %	Lines
src/App/src/Migration/Version20260907163051.php	0.00%	6 Missing ⚠️
src/App/src/Fixture/PostLoader.php	0.00%	5 Missing ⚠️
src/Blog/src/Entity/Post.php	0.00%	5 Missing ⚠️
src/Blog/src/Handler/GetPostResourceHandler.php	85.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               live     #209      +/-   ##
============================================
+ Coverage     59.85%   60.64%   +0.78%     
- Complexity      541      558      +17     
============================================
  Files            85       91       +6     
  Lines          2115     2185      +70     
============================================
+ Hits           1266     1325      +59     
- Misses          849      860      +11     

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