feat: format deploy and renovate notifications

[ineedjet]

🤖 [rubykatzen/flightdeck]:

Summary

• format deploy and renovate Telegram notifications with a bold repository and target plus a link to the Actions run
• group renovated apps by host using a structured updated-items output while retaining updated-hosts
• expose the prepared MarkdownV2 message directly from the deploy and renovate actions; workflows only send it and retain ownership of Telegram credentials
• keep escaping, validation, and Telegram message-length handling in a shared internal formatter
• update workflow and action documentation

Testing

• python3 -m unittest discover -s .github/actions/deploy/tests -v (55 tests)
• python3 -m unittest discover -s .github/actions/renovate/tests -v (13 tests)
• python3 -m unittest discover -s .github/actions/telegram-message/tests -v (7 tests)
• pre-commit run --all-files

📨 🧪 ✅