fix: avoid invalid secret checks in release workflow

[orangeboyChen]

Summary

• repair the release workflow so GitHub Actions accepts the file again
• detect Docker Hub credentials in a shell step and gate Docker Hub login from that output
• keep the existing behavior of pushing latest/version tags to GHCR and optionally to Docker Hub

Root cause

• PR ci: publish latest releases to ghcr and dockerhub #17 used a secrets-based expression directly in a step-level if condition
• GitHub rejected the workflow before jobs were created and marked the run as a workflow file issue

Verification

• bun run lint
• bun run format:check
• bun run typecheck
• bun run test:coverage
• bun run build

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.74%. Comparing base (609c9dd) to head (9ec1ac8).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #18   +/-   ##
=======================================
  Coverage   91.74%   91.74%           
=======================================
  Files          12       12           
  Lines        4770     4770           
  Branches      978      978           
=======================================
  Hits         4376     4376           
  Misses        385      385           
  Partials        9        9           

Flag	Coverage Δ
unittests	91.74% <ø> (ø)

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