ci: update some workflows

[shamaton]

summary

• validate go.mod with Dependabot
• add labeler workflow
• add CODEOWNERS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.57%. Comparing base (66d8cc6) to head (3b66ae3).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #84   +/-   ##
=======================================
  Coverage   95.57%   95.57%           
=======================================
  Files          73       73           
  Lines        6366     6366           
=======================================
  Hits         6084     6084           
  Misses        167      167           
  Partials      115      115           

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