feat: add git-ref parameter to support deploying from specific branches

[maoanran]

Add git-ref input parameter to deploy workflows to enable building and deploying from specific git refs (branches, tags, or SHAs). This enables PR comment-based deployments where the PR branch needs to be checked out and built.

Changes

• Add git-ref input to component-build.yml and update checkouts to use it
• Add git-ref input to deploy-generic.yml, deploy-generic-v2.yml
• Add git-ref input to deploy-kotlin.yml, deploy-python.yml
• Update image-tag output to use actual checked-out SHA instead of github.sha

Use case

Enables workflows like:

on:
  issue_comment:
    types: [created]

jobs:
  get-pr-ref:
    # ... get PR branch ref
  deploy:
    uses: monta-app/github-workflows/.github/workflows/deploy-generic.yml@main
    with:
      git-ref: ${{ needs.get-pr-ref.outputs.ref }}
      # ... other params

Backwards compatible

The git-ref parameter is optional and defaults to the triggering ref, so existing workflows continue to work without changes.