Implements multi-tenant infrastructure for organization-based data isolation.
Feature is gated behind PULSE_MULTI_TENANT_ENABLED env var and requires
Enterprise license - no impact on existing users.
Core components:
- TenantMiddleware: extracts org ID, validates access, 501/402 responses
- AuthorizationChecker: token/user access validation for organizations
- MultiTenantChecker: WebSocket upgrade gating with license check
- Per-tenant audit logging via LogAuditEventForTenant
- Organization model with membership support
Gating behavior:
- Feature flag disabled: 501 Not Implemented for non-default orgs
- Flag enabled, no license: 402 Payment Required
- Default org always works regardless of flag/license
Documentation added: docs/MULTI_TENANT.md
