docs: sync workspace docs with Angular 20, zoneless, EntityCache TTL/SWR, Sentry & ESLint boundaries

- PROJECT.md: stack bumped (Angular 20.3, TS 5.9, cdk/material 20, CLI/ng-packagr 20, Node >=20, esbuild builder); zoneless; ESLint flat-config + boundaries; Sentry in observability row; EntityCache TTL/SWR
- architecture.md: EntityCache TTL/SWR, app.config (zoneless + Sentry ErrorHandler), observability section, boundaries enforcement, main.ts initSentry
- shared.md: EntityCache TTL/SWR API
- core/services.md: GlobalErrorHandler no longer registered (replaced by Sentry), WebsocketService.connectionLost$
- cross-cutting.md: new connection-status package

Author: Awakich