Server Actions

### Which @angular/* package(s) are relevant/related to the feature request?

platform-server

### Description

It would be cool to create a way to server functions, just like a next.js resource called server actions.

### Proposed solution

It would be cool to create a way to server functions, just like a next.js resource called server actions.

### Alternatives considered

Create a annotation for execute server functions

Start by reviewing the platform-server package and the Next.js server actions reference named in the issue. Resolve whether the goal is server functions or an annotation before implementation; no file, test, or concrete acceptance criteria are provided, so done requires an agreed scope and testable behavior.

索引モデルが issue の本文から書いたものです。