chore(deps): update gitroomhq/postiz-app to v2.16.0 (#3859)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| ghcr.io/gitroomhq/postiz-app | minor | `v2.15.0` → `v2.16.0` |
| [gitroomhq/postiz-app](https://github.com/gitroomhq/postiz-app) | minor | `v2.15.0` → `v2.16.0` |

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### Release Notes

<details>
<summary>gitroomhq/postiz-app (gitroomhq/postiz-app)</summary>

### [`v2.16.0`](https://github.com/gitroomhq/postiz-app/releases/tag/v2.16.0): Schedule Forum Posts to Whop

[Compare Source](https://github.com/gitroomhq/postiz-app/compare/v2.15.1...v2.16.0)

You can now add Whop to Postiz and schedule Forum Posts

**Full Changelog**: <https://github.com/gitroomhq/postiz-app/compare/v2.15.1...v2.16.0>

### [`v2.15.1`](https://github.com/gitroomhq/postiz-app/releases/tag/v2.15.1): General Fixes

[Compare Source](https://github.com/gitroomhq/postiz-app/compare/v2.15.0...v2.15.1)

- Fixes for AI agents and an upgrade to GPT 5.1
- LinkedIn Carousel fixes
- Show file name on uploaded media

**Full Changelog**: <https://github.com/gitroomhq/postiz-app/compare/v2.15.0...v2.15.1>

</details>

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### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about these updates again.

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 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

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This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
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Reviewed-on: #3859
Co-authored-by: Renovate Bot <renovate-bot@alexlebens.net>
Co-committed-by: Renovate Bot <renovate-bot@alexlebens.net>

clusters/cl01tl/helm/postiz/Chart.yaml

@@ -41,4 +41,4 @@ dependencies:
     repository: oci://harbor.alexlebens.net/helm-charts
 icon: https://cdn.jsdelivr.net/gh/selfhst/icons/png/postiz.png
 # renovate: datasource=github-releases depName=gitroomhq/postiz-app
-appVersion: v2.15.0
+appVersion: v2.16.0