Add VPS IMAP sorting automation

Prompts used since the previous commit:
- Hieronder staat je oorspronkelijke plan. Volgens mij moet stap 'Add VPS automation' nog worden uitgevoerd, inclusief de testen.

Special observations:
- Added a testable IMAP sorting daemon, shared IMAP operation helpers, systemd service template, and SSH deployment script.
- Local tests passed; no live VPS deployment or mailbox-affecting daemon test was run.
- verplaats_log.json remains modified from the user's run and was intentionally not staged.

.gitignore

@@ -4,3 +4,5 @@ __pycache__/
 .DS_Store
 config.json
 **/*.eml
+sort_mail_daemon_state.json
+verplaats_log_*.json