feat: fix CI publish step: replace deprecated pub action with dart pub publish

[Copilot]

The sakebook/actions-flutter-pub-publisher@v1.3.1 action fails with pub: not found because it expects the standalone pub command removed in Dart 3.x.

Changes

• Replace deprecated action with native dart pub publish --force
• Set up credentials via $HOME/.config/dart/pub-credentials.json (standard Dart credential location)
• Remove redundant dry-run step

- name: Setup Pub Credentials
  run: |
    mkdir -p $HOME/.config/dart
    echo '${{ secrets.PUB_CREDENTIALS }}' > $HOME/.config/dart/pub-credentials.json

- name: Publish to pub.dev
  run: dart pub publish --force

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[bug] fix CI error</issue_title>
<issue_description>see: https://github.com/casbin/dart-casbin/actions/runs/19476251913/job/55736782632

Run sakebook/actions-flutter-pub-publisher@v1.3.1
  with:
    credential: ***
    flutter_package: false
    skip_test: true
    dry_run: false
  env:
    PUB_ENVIRONMENT: bot.github
    DART_HOME: /opt/hostedtoolcache/dart/3.10.0/x64
    PUB_CACHE: /home/runner/.pub-cache
/usr/bin/docker run --name da4a1ed2343d4073da44dc8fb5cedd48c213a4_64a678 --label da4a1e --workdir /github/workspace --rm -e "PUB_ENVIRONMENT" -e "DART_HOME" -e "PUB_CACHE" -e "INPUT_PACKAGE_DIRECTORY" -e "INPUT_CREDENTIAL" -e "INPUT_FLUTTER_PACKAGE" -e "INPUT_SKIP_TEST" -e "INPUT_DRY_RUN" -e "HOME" -e "GITHUB_JOB" -e "GITHUB_REF" -e "GITHUB_SHA" -e "GITHUB_REPOSITORY" -e "GITHUB_REPOSITORY_OWNER" -e "GITHUB_REPOSITORY_OWNER_ID" -e "GITHUB_RUN_ID" -e "GITHUB_RUN_NUMBER" -e "GITHUB_RETENTION_DAYS" -e "GITHUB_RUN_ATTEMPT" -e "GITHUB_ACTOR_ID" -e "GITHUB_ACTOR" -e "GITHUB_WORKFLOW" -e "GITHUB_HEAD_REF" -e "GITHUB_BASE_REF" -e "GITHUB_EVENT_NAME" -e "GITHUB_SERVER_URL" -e "GITHUB_API_URL" -e "GITHUB_GRAPHQL_URL" -e "GITHUB_REF_NAME" -e "GITHUB_REF_PROTECTED" -e "GITHUB_REF_TYPE" -e "GITHUB_WORKFLOW_REF" -e "GITHUB_WORKFLOW_SHA" -e "GITHUB_REPOSITORY_ID" -e "GITHUB_TRIGGERING_ACTOR" -e "GITHUB_WORKSPACE" -e "GITHUB_ACTION" -e "GITHUB_EVENT_PATH" -e "GITHUB_ACTION_REPOSITORY" -e "GITHUB_ACTION_REF" -e "GITHUB_PATH" -e "GITHUB_ENV" -e "GITHUB_STEP_SUMMARY" -e "GITHUB_STATE" -e "GITHUB_OUTPUT" -e "RUNNER_OS" -e "RUNNER_ARCH" -e "RUNNER_NAME" -e "RUNNER_ENVIRONMENT" -e "RUNNER_TOOL_CACHE" -e "RUNNER_TEMP" -e "RUNNER_WORKSPACE" -e "ACTIONS_RUNTIME_URL" -e "ACTIONS_RUNTIME_TOKEN" -e "ACTIONS_CACHE_URL" -e "ACTIONS_RESULTS_URL" -e GITHUB_ACTIONS=true -e CI=true -v "/var/run/docker.sock":"/var/run/docker.sock" -v "/home/runner/work/_temp/_github_home":"/github/home" -v "/home/runner/work/_temp/_github_workflow":"/github/workflow" -v "/home/runner/work/_temp/_runner_file_commands":"/github/file_commands" -v "/home/runner/work/dart-casbin/dart-casbin":"/github/workspace" da4a1e:d2343d4073da44dc8fb5cedd48c213a4
Check credentials
OK
Copy credentials
OK
Switching to package directory
Skip test
Executing package validation
/home/cirrus/entrypoint.sh: 63: pub: not found

```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes [bug] fix CI error #76

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