⚙️ Create @codechu/flow-core-config package

Design and implement configuration management abstractions:

## Interfaces to Create:
- `IFlowConfig` - Configuration access interface
- `IFlowConfigProvider` - Configuration loading interface  
- `IFlowConfigSection<T>` - Typed configuration sections

## Priority: 🟠 High
## Effort: S (1-2 days)
## Dependencies: @codechu/flow-core-seed only