Add Dependabot auto-merge workflow and migration script

[Marenz]

Summary

• Adds auto-merge workflow for Dependabot PRs using frequenz-floss/dependabot-auto-approve action
• Includes migration script to create workflow file and disable CODEOWNERS review requirement via GitHub API
• Splits changes into two commits: reset migration script to template, then add new migration steps

Changes

First commit: Reset cookiecutter/migrate.py to template, removing old migration steps

Second commit:

• Add create_dependabot_auto_merge_workflow() function
• Add disable_codeowners_review_requirement() function to update GitHub rulesets
• Include workflow template in cookiecutter
• Regenerate golden test files

[Copilot]

Pull Request Overview

This PR adds Dependabot auto-merge functionality to streamline dependency updates. It creates a GitHub Actions workflow to automatically merge Dependabot PRs and updates the migration script to create this workflow and disable the CODEOWNERS review requirement for automated merges.

Key changes:

• Added new auto-dependabot.yaml workflow for automatic Dependabot PR merging
• Updated migration script to create the workflow and modify GitHub ruleset settings
• Added/updated lockfile (uv.lock) with project dependencies

Reviewed Changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 5 comments.

File	Description
uv.lock	Added complete dependency lockfile with pinned versions
auto-dependabot.yaml (multiple)	New GitHub Actions workflow for auto-merging Dependabot PRs
cookiecutter/migrate.py	Refactored migration script to create auto-merge workflow and disable CODEOWNERS requirement

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[Marenz]

While testing in the FCR Repo I found it still didn't work and added the fix you see here, after which it finally worked

[Marenz]

Adds auto-merge: 'true' to the Dependabot workflow template.

Migration script fixes:

• Was skipping existing files instead of updating them
• Was matching job name auto-merge: instead of parameter auto-merge: 'true'
• Only checked auto-dependabot.yaml, now searches all workflow files

The script writes the updated workflow file directly - users still need to review, commit with DCO+GPG, and create a PR.

[Marenz]

Updated the branch with some refactoring and cleanup:

• Refactored the migration script by extracting helper functions (get_default_branch(), find_version_branch_ruleset(), update_ruleset()) for better code organization and error handling
• Improved error messages with proper manual_step() calls that provide direct GitHub settings URLs when API operations fail
• Standardized the Dependabot workflow formatting across all templates and golden test files (consistent naming, label changed to tool:auto-merged, YAML formatting)
• Fixed the release notes - they were accidentally removed in the previous iteration, now properly documenting the new auto-merge feature
• Removed uv.lock that shouldn't have been committed

[llucax]

2 small comments, feel free to force-merge if you want to fix them.

[llucax]

Nitpick: To avoid any other issues with template interpretation, other workflows actually just wrap the whole file between {% raw %} and {% endraw %}, maybe it would be better to do it in this file too, as it would be rare that we want to use any other template features in it.

[llucax]

Nitpick: Print the exception for more context of why it failed?