Add optional excludeUserID parameter to GetTimeBlockersInRange and CheckTimeBlockerOverlap so a user's own RESERVATION entries are excluded from overlap checks. This prevents users from self-blocking on their existing reservation when checking availability or confirming a booking. Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>