fix: CI Gate checks Codecov status when backend tests ran

[fiddur]

Summary

• CI Gate now verifies Codecov status checks (codecov/patch and codecov/project) when the node job ran
• When node is skipped (Android-only changes), the Codecov check is skipped entirely — solving the issue where Codecov doesn't post any status when no backend changes are made
• Polls the GitHub commit status API with a 5-minute timeout (30 x 10s) as a safety valve for Codecov outages

How it works

Scenario	CI Gate behavior
Backend changed, codecov passes	Gate passes
Backend changed, codecov/patch fails	Gate fails
Backend changed, codecov never reports (outage)	Gate warns but passes after 5min
Only Android changed	Codecov step skipped entirely
Only web changed (no backend)	Node job still runs but codecov uploads; gate checks codecov

This allows removing codecov/patch and codecov/project from the branch protection required checks — CI Gate handles it conditionally.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 31.43%. Comparing base (f73c291) to head (ed92805).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #283   +/-   ##
========================================
  Coverage    31.43%   31.43%           
========================================
  Files          181      181           
  Lines        22986    22986           
  Branches      1856     1856           
========================================
  Hits          7225     7225           
  Misses       15727    15727           
  Partials        34       34           

Flag	Coverage Δ
backend	58.08% <ø> (ø)

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