[Feature] Add GitHub Actions Workflow Support

### Is there an existing feature request for this?

- [x] I have searched the existing issues

### Describe the Feature

Enhance the existing data model by integrating GitHub Actions workflow data available via the Fivetran GitHub connector. Specifically, incorporate the `workflow`, `workflow_run`, and `workflow_pull_request` tables to provide visibility into CI/CD health and performance.

GitHub Actions is a critical part of modern software delivery, powering automated testing, deployments, and other CI/CD workflows. Despite this, the current data model does not expose any workflow-related metrics or insights.

By integrating workflow data into the model, teams can:
- Monitor workflow success/failure trends
- Identify performance bottlenecks in builds and deployments
- Correlate failing workflows with specific PRs, users, and branches
- Improve developer efficiency and reduce time to resolution for workflow-related issues

### How would you implement this feature?

Create staging models:
- stg_github__workflow
- stg_github__workflow_run
- stg_github__workflow_pull_request

Create an intermediate `int_github__workflow_summary` model. Aggregates and summarizes workflow execution activity at the repository and workflow level. Example Fields:
- repo_name
- workflow_name
- total_runs
- success_rate
- avg_duration_seconds
- failed_runs_last_7_days
- last_run_status

Finally a new end model `github__workflow_run_report` for enriched workflow run-level reporting. Joins workflow runs with pull requests and user metadata for context. This model would help support executive reporting on CI/CD health, provide insights into which PRs or branches introduce failing workflows, and drilldowns into long running or frequently failing workflows. Example Fields:
- repo_name
- workflow_name
- workflow_run_id
- status
- conclusion
- run_started_at
- duration_seconds
- pr_number
- pr_title
- pr_author

### Describe alternatives you've considered

_No response_

### Are you interested in contributing this feature?

- [ ] Yes.
- [ ] Yes, but I will need assistance.
- [ ] No.

### Anything else?

This feature would bring full visibility into a previously unmodeled but critical piece of the SDLC within GitHub: CI/CD workflows. It closes the loop from PR creation to automated testing and deployment, providing actionable insights for engineering and DevOps teams.