fix(ci): cancel obsolete pull request workflows

[Rello]

• Adds PR-scoped concurrency to all 15 pull-request workflows.
• Uses cancel-in-progress: true to cancel obsolete runs after new commits.
• Adds the closed activity so closing or merging a PR cancels its active runs.
• Prevents cancellation-only runs from executing jobs.
• Preserves separate concurrency for master push workflows.

note on the if-condition. this is used to cancel existing runs when a PR is closed

• Another commit creates a new run in the same group. Because cancel-in-progress: true, GitHub cancels the older run.
• Closing or merging the PR emits the newly enabled closed event. That creates another run in the same group, causing GitHub to cancel the active run.
• The job condition prevents the new close-event run from doing any work

Assisted-by: Codex:GPT-5

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Rello]

/backport to stable-34.0

[backportbot]

The backport to stable-34.0 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable-34.0
git pull origin stable-34.0

# Create the new backport branch
git checkout -b backport/10715/stable-34.0

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick da8d45b3

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/10715/stable-34.0

Error: Failed to clone repository: Failed to create working tree: error: RPC failed; HTTP 401 curl 22 The requested URL returned error: 401
fatal: expected flush after ref listing

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.