chore(deps): update actions/checkout action to v6

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| ghcr.io/renovatebot/renovate | container | digest | `c695036` -> `0f129ba` |

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### Configuration

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

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

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update 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).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0Mi4xMS4wIiwidXBkYXRlZEluVmVyIjoiNDIuMTEuMCIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Reviewed-on: #47
Co-authored-by: Renovate Bot <renovatebot@schulze.network>
Co-committed-by: Renovate Bot <renovatebot@schulze.network>

.gitea/workflows/renovate.yaml

@@ -10,7 +10,7 @@ on:
 jobs:
   renovate:
     runs-on: ubuntu-latest
-    container: ghcr.io/renovatebot/renovate:latest@sha256:c6950364d634f956a88238f46510f6a9a77809f3d4427c68110b7bd750afc759
+    container: ghcr.io/renovatebot/renovate:latest@sha256:0f129ba37673d828fd03de6a9dd548492bfb7a11da33245c43cbb5a1078a8bab
     steps:
       - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6
       - run: renovate