[PM-41894] Fix conflicting Renovate docker checks

[jprusik]

🎟️ Tracking

PM-41894

📔 Objective

The default docker Renovate manager is resulting in multiple docker-compose dependency checks

Because this can result in circular version bumping, and because we want to favor hash pinning over tags which are not immutable, we need to drop the default docker manager config in favor of the custom one for this project.

📸 Screenshots

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

This PR narrows .github/renovate.json by dropping the built-in dockerfile and docker-compose managers in favor of the existing custom.regex manager, and migrates the deprecated fileMatch key to managerFilePatterns. No Dockerfile exists in the repository, so removing the dockerfile manager loses no coverage, and both image: entries in docker-compose.yml (digest plus # <version> comment) still satisfy the custom manager's matchStrings pattern, preserving digest-pinned update behavior. The managerFilePatterns value uses the documented /regex/ delimited form and resolves to the same path matching as the previous fileMatch glob-style regex. The packageRules entry was correctly reduced to custom.regex, and no other rule, workflow, or config file references the removed managers.

Code Review Details

No findings.