Refactor: Rename GitHub repository node fields to recent_issues and recent_releases

**Is your feature request related to a problem? Please describe.**
While reviewing the backend codebase, I noticed two pending TODO comments from `@arkid15r` in `backend/apps/github/api/internal/nodes/repository.py` (lines 51 and 82). The current field names (`issues` and `releases`) do not accurately reflect that they are limited to recent items.

**Describe the solution you'd like**
As requested in the TODOs, rename the `issues` field to `recent_issues` and the `releases` field to `recent_releases` for better API clarity and consistency.

**Describe alternatives you've considered**
N/A - This is a direct implementation of existing TODO comments left by a maintainer.

**Are you going to work on implementing this?**

- [x] Yes
- [ ] No

**Additional context**
I have already made these changes on my local branch. Could a maintainer please assign this issue to me? I am ready to open the Pull Request immediately upon assignment!