Update/robustify the release scripts for subpackages (apache-hamilton-*)

[Dev-iL]

This PR contains QoL improvements and fixes to various issues encountered while verifying the apache-hamilton-{sdk,ui,lsp,contrib} packages in the context of https://lists.apache.org/thread/d4fzmqq4jbsx5m3krdp1qbr0wh9j131s and related threads.

Includes #1612

Changes

UI Package (apache-hamilton-ui)

• Added README.md for the ui/backend package, fixing long_description/long_description_content_type warnings during flit build
• Frontend build step: the release script now runs npm run build and copies compiled frontend assets into hamilton_ui/build/ before building the wheel, ensuring the UI package includes its frontend (from Add frontend build step to UI release process #1612)
• npm audit fix: resolved one moderate severity vulnerability in frontend dependencies

Release Helper (scripts/apache_release_helper.py)

• --no-sign / -ns: skips GPG signing; implicitly also skips upload since unsigned artifacts must never be published
• --no-upload / -nu: skips git tagging and SVN upload while still signing; useful for rehearsing the full signing step without publishing
• apache_id is no longer required when --no-upload (or --no-sign) is set
• uv script dependencies declared in the PEP 723 inline metadata block so the script can be run with uv run

Verification Scripts (scripts/verify-sub-packages/)

• cd /tmp before functional checks in all four verify scripts (verify_contrib.sh, verify_sdk.sh, verify_lsp.sh, verify_ui.sh): prevents Python's implicit '' (cwd) sys.path entry from resolving the local checkout instead of the venv-installed packages when the script is run from the repo root
• More informative error in verify_ui.sh: improved diagnostics when the UI health-check endpoint is unreachable
• uvx flit used in place of a separately installed flit across all verify scripts
• TOML verification pre-commit hook added to ui/sdk/.pre-commit-config.yaml

How I tested this

After introducing these changes I could successfully run the verification shell scripts for all distributions as well as uv run scripts/apache_release_helper.py --package {pkg} {ver} 0 -ns

Notes

I had include the version bump commit so that apache_release_helper.py runs correctly (with the new versions). We might want to consider making the version mismatch non-fatal when building packages with no intention to upload them.

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.