Extends the existing PATCH /admin/agents/:agentId with an optional userId
to finish wiring 010's Agent.userId link, and adds GET /agents/me/tickets
+ GET /admin/agents/:agentId/tickets sharing one ticketing/tickets service
method, backed by a new Assignment @@index([agentId, isCurrent]).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>