chore: add Dependabot configuration

[andres-qd]

Dependabot Configuration

Adds automated dependency management via Dependabot.

Detected ecosystems

• cargo
• docker

Configuration

• Schedule: weekly
• PR limit: 5 per ecosystem
• Grouping: security updates grouped together, minor/patch version updates grouped together, major updates ungrouped
• Target branch: master

What to expect

• Dependabot will open PRs for dependency updates based on the schedule above
• Security updates are prioritized and grouped separately
• Major version updates appear as individual PRs (may have breaking changes)

Customize this config after merging if your repo has specific needs (e.g., custom registries, multiple directories, ignore rules).

[timvisee]

Please target the dev branch instead