VS Crews

Crew system for Valkyrien Skies + Eureka.
Create crews, manage members, and enforce helm usage/break/builder rules via server config.

Core behavior
- Helm use/break is gated by crew membership
- Helms placed by non-crew players follow configurable rules (usable by everyone vs placer-only)
- Helms referencing deleted crews behave like no-crew helms
- Ships being unbreakable by non-crew members (only breakably using M1)
- config for breaking will come later

Commands (type /vscrew)
- create <name> — create a crew (case-insensitive unique names)
- info [crew] — show owner & members (names); no-arg when one-crew rule is enabled
- add/remove <crew> <player> — manage members (optional: allow members to manage via config; owner-only otherwise)
- delete [crew] — owner-only; removes a crew; no-arg when one-crew rule is enabled
- leave [crew] — non-owner can leave; no-arg when one-crew rule is enabled
- rename <crew> <newName> — owner-only; case-insensitive uniqueness enforced