chore: upgrading fastify to 5.6.1

[jaredwray]

Please check if the PR fulfills these requirements

• Followed the Contributing guidelines.
• Tests for the changes have been added (for bug fixes/features) with 100% code coverage.

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
chore: upgrading fastify to 5.6.1

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (4f9d75f) to head (f6a55b0).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #84   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           36        36           
  Lines         2027      2027           
  Branches       154       154           
=========================================
  Hits          2027      2027           

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