Buildbear workflow integration

[itsshantanu]

This pull request introduces a new modular GitHub Actions CI workflow system for the project using Buildbear Labs, focused on improving maintainability and reusability for module-based development. The main changes include adding a reusable workflow for CI jobs and a specific workflow for the flow module, both of which leverage shared logic and external reusable workflows.

CI Workflow Infrastructure Improvements:

• Added .github/workflows/bb-ci-module.yml, a reusable workflow that defines a comprehensive set of jobs (check, build, various test types, and coverage) for any given module, with configurable inputs for test exclusions and module selection. This workflow uses shared actions from sablier-labs/gha-utils for consistency and maintainability.
• Introduced .github/workflows/bb-ci-flow.yml, a workflow specifically for the flow module, which delegates its jobs to the reusable bb-ci-module.yml workflow and configures it to exclude unit tests. It is triggered on relevant changes and supports concurrency to avoid overlapping runs.
• This PR is linked to this PR https://github.com/sablier-labs/gha-utils/pull/50