#64 API: Update Tenant

Implement endpoint to update tenant settings. Endpoint: PATCH /api/v1/tenants/{tenant_id} Request Body: - display_name: string (optional) - settings: object (optional) - status: string (optional: active, suspended) Response: Updated tenant object Required Permissions: system_admin, or tenant_admin for own tenant (limited fields) Implementation Requirements: - Validate tenant exists - tenant_admin can only update display_name and settings - system_admin can update status - Suspending tenant invalidates all sessions - Log all changes to audit trail With ultra attention to details and correctness. Before closing: write comment summarizing implementation with screenshot.