Update compatibility hints for multiple servers

- CCS (Apple CalendarServer): add full test server setup; document
  cross-calendar UID enforcement and min-date-time restrictions
- Zimbra: add search.text.substring unsupported hint; update several hints
  following actual test runs
- Cyrus: update hints; set password to sentinel (any password accepted)
- Bedework: remove stale workaround hints after GET-on-items started working
- purelymail: correct search.time-range.todo (was a false negative due to
  caching); increase post-write delay to 300 s; update after full test run
- GMX: fix typo; mark create-calendar as unknown
- ecloud: remove create-calendar unsupported hint (feature works)
- posteo: fix several hints that were false negatives
- General: add search.is-not-defined.category / .dtend sub-features;
  fix parent-feature defaults not being overridden by subfeature derivation;
  fix duplicate certificate-detection logic

Co-Authored-By: Claude <noreply@anthropic.com>

Author: tobixen