Add Human-in-the-Loop interrupt support for interactive workflows

Summary

Implement a comprehensive Human-in-the-Loop (HIL) system that enables workflows to pause execution and request user input before continuing. This feature is essential for building interactive workflows that require human decision-making, approval gates, or data collection during execution.

Business Value

• Enables building approval workflows where human oversight is required at critical decision points
• Supports interactive chatbot and conversational AI use cases
• Allows workflows to collect additional information from users mid-execution
• Provides audit trail showing who responded to each interrupt and when

Features Implemented

• Confirmation Node: Simple Yes/No prompts for user decisions
• Choice Input Node: Selection from multiple options (single or multi-select)
• Text Input Node: Free-form text collection with validation
• Form Input Node: JSON Schema-based forms for structured data collection

Technical Implementation

• New flowdrop_interrupt module with persistent interrupt entity storage
• Exception-based interrupt handling working across all pipeline-based orchestrators
• RESTful API endpoints for listing, resolving, and canceling interrupts
• New job status "interrupted" with proper lifecycle transitions
• Full integration with FlowDrop Playground UI

Supported Orchestrators

• Synchronous Pipeline Orchestrator
• Asynchronous Orchestrator
• StateGraph Orchestrator