🔄 Create @codechu/flow-core-workflow package

[obarlik]

Design and implement workflow orchestration abstractions:

Interfaces to Create:

• IFlowWorkflow<TIn, TOut> - Workflow execution interface
• IFlowWorkflowBuilder - Workflow construction interface
• IFlowWorkflowStep - Enhanced step with conditions/retry
• IFlowWorkflowContext - Workflow-specific context

Priority: 🟡 Medium

Effort: L (1-2 weeks)

Dependencies: @codechu/flow-core-seed + infrastructure packages