chore: Add information for contributors about next gen (#12741)

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# Which Problems Are Solved

Currently the state for contributions is not clear to community
contributors.

# How the Problems Are Solved

Added a note to the contribution.md and the pr template

(cherry picked from commit 20d79ca05e)

.github/pull_request_template.md

@@ -3,6 +3,9 @@ Please inform yourself about the contribution guidelines on submitting a PR here
 Important: By submitting a contribution you agree to the terms from our Licensing Policy as described here: https://github.com/zitadel/zitadel/blob/main/LICENSING.md#community-contributions.
 -->
 
+> [!IMPORTANT]
+> Our engineering team is currently focused on the [next generation of ZITADEL](https://github.com/zitadel/nextgen), so our capacity to review community pull requests is limited. We cannot guarantee that your pull request will be reviewed or merged. For larger changes, please open an issue or discussion before you begin. Thank you for contributing and for your understanding.
+
 # Which Problems Are Solved
 
 Replace this example text with a concise list of problems that this PR solves.

CONTRIBUTING.md

@@ -1,5 +1,10 @@
 # Contributing to Zitadel
 
+> [!IMPORTANT]
+> Thank you for contributing to ZITADEL. Our engineering team is currently focused on building the [next generation of ZITADEL](https://github.com/zitadel/nextgen), which means our capacity to review community pull requests for the current codebase is limited.
+> We cannot guarantee that a pull request will be reviewed or merged, even if it is well prepared. Before investing time in a larger change, please open an issue or discussion so we can confirm whether it aligns with our current direction.
+> We truly appreciate your contributions and your understanding.
+
 Zitadel is an open-source identity and access management platform built with a modern tech stack including Go (API), Next.js/React (Login), Angular (Console), and Fumadocs (Docs) - all orchestrated through an Nx monorepo with pnpm for efficient development workflows.
 
 ## Quick Start