fix: repair v0.7.1 release packaging

[atomize-lab]

Summary

• install and invoke PyInstaller explicitly, with deterministic Windows output paths
• set the Windows health-check port before launching the packaged server
• flatten the Linux bundle's scripts/ layout so ci_common is importable
• add cross-platform release contract tests and update v0.7.1 notes

Root-cause evidence

Failed release run: https://github.com/atomize-lab/citeseal/actions/runs/29716705069

• Windows: pyinstaller was not installed or available on PATH
• Linux: tools/scripts was copied into an already-created scripts/ directory, producing scripts/scripts/ and ModuleNotFoundError: ci_common

Validation

• RED: all 3 release contract tests failed before the fix
• GREEN: 223 passed on Python 3.13 locally
• Linux tarball built, extracted, and returned HTTP 200 from /api/health
• release workflow YAML parses; shell script passes bash -n; focused pyflakes and git diff --check pass