[Feature] Native support for GitHub App authentication (x-access-token) for push/pull operations

[PeterDurrer]

Describe the problem

I want to integrate Weblate with GitHub using a GitHub App instead of a personal access token (PAT) or SSH deploy key. This would allow secure, organization-wide access to repositories without creating a dedicated GitHub user or managing long-lived credentials. GitHub Apps are the recommended way to automate workflows and offer short-lived tokens, scoped permissions, and centralized control.

Solution brainstorm

• Add GitHub App as a first-class authentication method in Weblate
• Allow configuration of App ID, Installation ID, and .pem private key
• Automatically generate JWT and fetch installation tokens
• Use x-access-token: for HTTPS Git operations
• Support global configuration or per-component overrides
• Optionally integrate a built-in Git credential helper or token proxy
• Enable webhook auto-detection for GitHub App installations

Describe alternatives you have considered

No response

Screenshots

No response

Additional context

GitHub Apps are widely used in CI/CD workflows (e.g. AL-Go, GitHub Actions) and offer better security than PATs. Weblate currently requires either a GitHub user with PAT or SSH keys, which is not ideal for organizations. Related discussions and issues:

• GitHub App authentication docs
• Weblate issues: GitHub integration #1688, Using Self-Hosted Weblate instance with GitHub repos from an internal GitHub Enterprise (SaaS) org #13835

[nijel]

The GitHub integration is expected to cover this, I want to have it this year.