Built-in authentication and authorization for Manticore Search

Manticore Search now includes built-in authentication and authorization starting with the 27.x release line. The feature covers SQL/MySQL clients (username/password), HTTP clients (Basic auth or Bearer tokens), distributed remote agents, and replication operations. The authorization model defines five actions — read, write, schema, replication, and admin — applied to named targets or wildcards. This replaces common workarounds like putting nginx in front of Manticore for access control. For SaaS and shared search deployments, it enables per-user permission boundaries, audit logging, and compliance-friendly controls (GDPR, SOC 2). Rollout guidance is provided: auth is disabled by default, and existing deployments should update clients and test before enabling in production. Distributed topologies should upgrade remote agents and replication peers before enabling auth on masters.