Implement configurable DNS resolver

[fifthsegment]

Summary

• make DNS resolver configurable in backend and default to 8.8.8.8:53
• expose new dns_resolver setting via API and UI
• allow updating resolver while server is running
• document DNS resolver configuration

Testing

• go test ./... (fails: connection resets and missing lsof)

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https://chatgpt.com/codex/tasks/task_b_686fb18591f08324b48d3abf5e0384b9

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.10%. Comparing base (c22cdbd) to head (ddfbe41).
Report is 4 commits behind head on master.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #110   +/-   ##
=======================================
  Coverage   70.10%   70.10%           
=======================================
  Files           1        1           
  Lines         378      378           
=======================================
  Hits          265      265           
  Misses         92       92           
  Partials       21       21           

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[codiflow]

Just a short question – what prevents the PR from being merged? 😉

[fifthsegment]

Just a short question – what prevents the PR from being merged? 😉

just lack of time to dedicate to this project 😢