Fix Generate Database workflow blocked by protected main branch

## Problem
The `Generate Database SQLite file` workflow failed on release `v3.4` (run [33641023889](https://github.com/astrodbtoolkit/astrodb-template-db/actions/runs/33641023889/job/100283819293)).

The database generation and commit succeeded, but pushing to `main` failed with:

```text
GH006: Protected branch update failed for refs/heads/main.
Changes must be made through a pull request.
```

The workflow had `contents: write`, so this is a branch protection/ruleset restriction rather than a missing `GITHUB_TOKEN` permission.

## Requested resolution
Choose one of the following:

- Allow the automation actor (`github-actions[bot]`, or the configured PAT user) to bypass the pull-request requirement for `main`; or
- Update `.github/workflows/generate_db.yml` to push generated files to a branch and open a pull request instead of pushing directly to `main`.

Ensure the release-tag update step remains compatible with the chosen approach.