ci: vote and announcement email tooling

[andreahlert]

Part of #715

Problem

Vote emails, result emails, and release announcements are composed manually. The format varies between releases and it is easy to forget required information (SVN links, KEYS file link, changelog, etc.).

Solution

Add a lightweight email tooling script that:

1. Generates vote email from a Jinja2 template, pre-filled with:
   • Version and RC number
   • Links to SVN artifacts, PyPI RC package, and KEYS file
   • Changelog summary
   • Voting deadline (72h from now)
2. Generates result email from a template, with vote tally
3. Generates announcement email from a template
4. Outputs to stdout (or copies to clipboard) for the release manager to send

Acceptance criteria

• Vote email template (`scripts/templates/vote_email.j2`)
• Result email template (`scripts/templates/result_email.j2`)
• Announcement email template (`scripts/templates/announce_email.j2`)
• CLI command to generate each: `python scripts/apache_release.py vote-email --version 0.43.0 --rc 1`

[andreahlert]

@skrawcz low priority but figured I'd file it. _generate_vote_email() already covers the vote template, but we don't have result or announcement templates. thinking we could add those plus a CLI entry point so the whole email flow is python apache_release.py vote-email, result-email, announce-email. would that be useful for you or is copy-paste fine?

[hussain-s]

Please assign to me I can work on this one

[hussain-s]

Pull request for the issue 719 is in following PR.

[hussain-s]

Revision 2 submitted after addressing the github copilot comment