build: Update ubuntu Docker tag to v26

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
ubuntu	stage	major	24.04 → 26.04

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (ffb5801) to head (11cd38c).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #48   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           53        53           
  Lines          674       674           
=========================================
  Hits           674       674           

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