Update server limit enforcement to re-enable force-disabled servers when the
team is at or under its limit (`<= 0` condition).
Improve allowlist validation and matching by:
- supporting IPv6 CIDR mask ranges up to `/128`
- adding IPv6-aware CIDR matching in `checkIPAgainstAllowlist`
- normalizing/deduplicating redundant allowlist entries before saving
Add feature tests for `ServerLimitCheckJob` covering under-limit, at-limit,
over-limit, and no-op scenarios.
