ci: Update CI branch references and add v0.4

## Problem

CI workflow only triggers on [main, v0.2, v0.3]. Needs v0.4 added.

## Changes

1. Add v0.4 to branch triggers in ci.yml
2. Consider adding Dependabot configuration for dependency updates
3. Consider Python version matrix testing (3.10, 3.11, 3.12)

## Acceptance Criteria

- [ ] CI triggers on v0.4 branch
- [ ] Dependabot.yml configured (optional)