fix: move PR template to correct Gitea location (#6)

## Description

Gitea requires the pull request template to be at `.gitea/PULL_REQUEST_TEMPLATE.md` (as a file), not in a `.gitea/PULL_REQUEST_TEMPLATE/` directory.
This PR moves the template from `.gitea/PULL_REQUEST_TEMPLATE/default.md` to `.gitea/PULL_REQUEST_TEMPLATE.md` to ensure it works correctly with Gitea.

## Benefits

- The pull request template will now be automatically loaded when creating new PRs in Gitea.
- Follows Gitea's documented convention for PR templates.

## Checklist

- [x] Code follows conventional commit format.
- [x] Branch follows naming convention (`<type>/<description>`).
- [x] Tests pass (if applicable).
- [x] Documentation updated (if applicable).

Reviewed-on: #6
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

.gitea/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,32 @@
+---
+title: "<type>: <description>"
+---
+
+## Description
+
+<!--
+First, describe the context for the PR.
+Then, explain why the PR exists.
+Finally, in concise, sentence-long bullets, explain each change.
+-->
+
+### Decisions
+
+<!--
+List any major architectural decisions here.
+If none exist, omit this section.
+-->
+
+## Benefits
+
+<!--
+List any major benefits here.
+How would this PR improve the codebase/product?
+-->
+
+## Checklist
+
+- [ ] Code follows conventional commit format.
+- [ ] Branch follows naming convention (`<type>/<description>`).
+- [ ] Tests pass (if applicable).
+- [ ] Documentation updated (if applicable).