Stability checkpoint stable-v1.0.21 (svc) — Phase 4.2 coverage wave: 134 new tests across 14 files (CustomerEnrichmentController, CustomerDiagnosticsController, SecurityDemoController, ApiKeyAuthenticationFilter, AppUserDetailsService, CustomerEnrichHandler, CustomerEventListener, ReportParsers, MaintenanceEndpoint, DataInitializer, CreateCustomerRequest, PatchCustomerRequest, StartupTimingsController, AuthController, JwtAuthenticationFilter). Includes production bug fix: SecurityDemoController.corsInfo() NPE on missing Origin header (curl/same-origin probes were 500'ing — coalesced to placeholder string). Post-merge main pipeline #695 SUCCESS on f997cee.