#250 [PHASE 2] Add RBAC Permissions to High Priority Endpoints

Phase 2: Add @require_permission decorators to: 1. signals.py - manage_workflows permission 2. queries.py - view_workflows permission 3. monitoring.py - view_workflows permission + tenant isolation 4. analytics.py - view_analytics permission 5. schemas.py - manage_schemas permission 6. updates.py - manage_workflows permission