chore(deps): update docker/build-push-action action to v7 (#19)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [docker/build-push-action](https://github.com/docker/build-push-action) | action | major | `v6` → `v7` |

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### Release Notes

<details>
<summary>docker/build-push-action (docker/build-push-action)</summary>

### [`v7`](https://github.com/docker/build-push-action/compare/v6...v7)

[Compare Source](https://github.com/docker/build-push-action/compare/v6...v7)

</details>

---

### 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 becomes conflicted, or you tick the rebase/retry checkbox.

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

---

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

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My41Ni4xIiwidXBkYXRlZEluVmVyIjoiNDMuNTYuMSIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Reviewed-on: #19
Reviewed-by: Keli Grubb <keligrubb324@gmail.com>
Co-authored-by: Renovate Bot <renovate@keligrubb.com>
Co-committed-by: Renovate Bot <renovate@keligrubb.com>

.gitea/workflows/pr.yml

@@ -78,7 +78,7 @@ jobs:
         uses: docker/setup-buildx-action@v4
 
       - name: Build (dry run)
-        uses: docker/build-push-action@v6
+        uses: docker/build-push-action@v7
         with:
           context: .
           push: false

.gitea/workflows/push.yml

@@ -34,7 +34,7 @@ jobs:
         uses: docker/setup-buildx-action@v4
 
       - name: Build Docker image
-        uses: docker/build-push-action@v6
+        uses: docker/build-push-action@v7
         with:
           context: .
           load: true