[TASK] Migrate backport and documentation workflows to shared reusable workflows

[CybotTM]

Summary

Migrates both workflow files to shared reusable workflows from
TYPO3-Documentation/.github.

Changes

Workflow	Before	After
backport.yml	22 lines inline	reusable-backport.yml (5 lines)
documentation.yml	15 lines inline	reusable-test-documentation.yml (8 lines)

Benefits

• Single point of maintenance — action version updates happen centrally
• Consistent configuration — all documentation repos test rendering the same way
• No allow-list concerns — .github workflows are automatically trusted

Dependencies and merge order

• Depends on .github#4 (backport label_pattern fix)
• Depends on .github#2 (adds reusable-test-documentation.yml)

[garvinhicking]

(Please note this is a POC we should not merge as-is, because we'd first have to import the referenced repo into our own maintenance scope. Thanks a lot, this is very helpful for discussion!)

[CybotTM]

Updated for merged TYPO3-Documentation/t3docs-ci-deploy#56

[sarahmccarthy123]

Looks good:-)

[typo3-docs-backport-bot]

Backport failed for 13.4, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin 13.4
git worktree add -d .worktree/backport-258-to-13.4 origin/13.4
cd .worktree/backport-258-to-13.4
git switch --create backport-258-to-13.4
git cherry-pick -x e44cec63293478ac46d310b77dc1f3d0054a3c44

[typo3-docs-backport-bot]

Backport failed for 14.3, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin 14.3
git worktree add -d .worktree/backport-258-to-14.3 origin/14.3
cd .worktree/backport-258-to-14.3
git switch --create backport-258-to-14.3
git cherry-pick -x e44cec63293478ac46d310b77dc1f3d0054a3c44

[typo3-docs-backport-bot]

Backport failed or needs manual intervention.

Backport action outcome: success
Backport success output: false
Per target: 13.4=false 14.3=false
Created backport PRs: none

Workflow run: https://github.com/TYPO3-Documentation/TYPO3CMS-Tutorial-Editors/actions/runs/30550696396