Implement workflow system for semaphore ui

[fiftin]

GEMINI 3

Implement Workflow feature to allow chaining tasks into pipelines with conditional and parallel execution.

This PR introduces the core components for the Workflow system:

• New database models and migrations for workflows, nodes, links, and runs.
• REST API endpoints for managing workflows and triggering runs.
• A Go-based workflow execution engine that integrates with the existing TaskPool.
• A basic Vue.js frontend for workflow creation/editing (drag-and-drop nodes, link management) and viewing run history.

---

 

[cursor[bot]]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch. _{Learn more about Cursor Agents}