Remove hard-coded halos.local references

[mairas]

Overview

Remove hard-coded halos.local hostname references to comply with the workspace hostname policy.

Tracking issue: halos-org/halos#61

Violations

src/generate_container_packages/registry.py:
  94:        "# Using halos.local as the default hostname",
  106:        url = f"{protocol}://halos.local{path}"
  108:        url = f"{protocol}://halos.local:{port}{path}"

tests/test_registry.py:
  77:        assert 'url = "http://halos.local:8080/"' in result
  149:        assert 'url = "http://halos.local/"' in result
  160:        assert 'url = "https://halos.local/"' in result
  168:        assert 'url = "http://halos.local:8080/app"' in result

Fix

1. registry.py: Replace hard-coded hostname with a required configuration parameter
2. test_registry.py: Use a test configuration or parameterized hostname

Enforcement

A pre-commit hook has been added. Run .github/scripts/check-hardcoded-hostnames.sh to verify.