Introduce support for handling request signal abortions in the `AngularServerApp`. This is particularly useful in the development server integration where a 30-second timeout is enforced for requests/responses.
- Exposed several utility functions as private APIs to support the integration with the build system.
- Removed `isDevMode` and caching logic from `AngularAppEngine`. This was necessary to better handle updates when using Vite. Instead, `AngularServerApp` is now treated as a singleton to simplify management.
- Switched asset storage from an `Object` to a `Map` in the manifest for improved efficiency and consistency.
This refactor sets the groundwork for seamless wiring with the build system.
