backend/v2.4.0

This release brings several security, reliability, and usability improvements across Hanko’s authentication stack. It includes stronger passcode options, better key management integration, more robust auth flows in Hanko Elements, improved device trust handling, and expanded localization support:

## Alphanumeric passcodes
In addition to numeric passcodes, **Hanko** now supports optional **alphanumeric passcodes**. This increases entropy and makes passcode-based authentication more resilient against brute-force and guessing attacks.

## External key providers (AWS KMS)
Hanko’s token signing engine can now be configured to use external **HSMs and Key Management Systems**, currently only **AWS KMS** is supported. This allows teams with higher security requirements to keep signing keys fully managed outside of Hanko.

## Security notifications
Hanko now optionally sends **email notifications for security-relevant actions** (enabled by default), for example when a new passkey is added to an account. These notifications help users detect suspicious activity early and improve overall account security.

## PKCE by default in Hanko Elements
Hanko Elements now uses **PKCE-based flows by default**. This resolves several issues with third-party integrations, especially in setups where the backend is not running on the same domain as the frontend.

## Multi-user device trust support
Device trust cookies are no longer overwritten on shared machines or when multiple users log into the same application. This improves reliability for **shared computers and multi-account setups** while keeping device trust intact per user.

## Dutch localization
Hanko now officially supports **Dutch (NL)**. This includes UI text, backend mailing templates, and security notification emails, providing a more complete localized experience for Dutch-speaking users.

## What's Changed
* feat: make elements use PKCE flow per default by @lfleischmann in https://github.com/teamhanko/hanko/pull/2365
* feat: add alphanumeric passcodes by @FreddyDevelop in https://github.com/teamhanko/hanko/pull/2334
* feat: add external key provider aws kms by @FreddyDevelop in https://github.com/teamhanko/hanko/pull/2342
* feat: add security notifications by @irby in https://github.com/teamhanko/hanko/pull/2312
* feat: add dutch translations by @Harm-Nullix in https://github.com/teamhanko/hanko/pull/2352
* feat: add dutch translations (backend mailing) by @Harm-Nullix in https://github.com/teamhanko/hanko/pull/2356
* feat: add dutch translations for security notifications by @lfleischmann in https://github.com/teamhanko/hanko/pull/2364
* feat: support multiple users per device for device trust by @fadlikadn in https://github.com/teamhanko/hanko/pull/2360
* ci: exclude examples from dependabot scan by @lfleischmann in https://github.com/teamhanko/hanko/pull/2369
* ci: fix dependabot exclude path for examples by @lfleischmann in https://github.com/teamhanko/hanko/pull/2375
* ci: fix dependabot exclude path again by @lfleischmann in https://github.com/teamhanko/hanko/pull/2376
* ci: make workflows ready for trusted publishing by @lfleischmann in https://github.com/teamhanko/hanko/pull/2313
* ci: update node in build frontend workflow by @lfleischmann in https://github.com/teamhanko/hanko/pull/2329
* chore: remove fresh example by @lfleischmann in https://github.com/teamhanko/hanko/pull/2328
* chore: update preact by @lfleischmann in https://github.com/teamhanko/hanko/pull/2337
* chore: autogenerate config JSON schema by @github-actions[bot] in https://github.com/teamhanko/hanko/pull/2344
* chore: autogenerate config JSON schema by @github-actions[bot] in https://github.com/teamhanko/hanko/pull/2346
* chore: autogenerate config JSON schema by @github-actions[bot] in https://github.com/teamhanko/hanko/pull/2363
* chore: autogenerate config JSON schema by @github-actions[bot] in https://github.com/teamhanko/hanko/pull/2366
* chore: update examples by @lfleischmann in https://github.com/teamhanko/hanko/pull/2345

## New Contributors
* @Harm-Nullix made their first contribution in https://github.com/teamhanko/hanko/pull/2352
* @fadlikadn made their first contribution in https://github.com/teamhanko/hanko/pull/2360

**Full Changelog**: https://github.com/teamhanko/hanko/compare/backend/v2.3.0...backend/v2.4.0