[Example] flow: quant-wiki flow impl (knowledge graph)

@USTCKevinF is already working on this.

Since Sep 1, 2025.

## ✨ Feature Summary

The task involves optimizing the workflow for building, enhancing, and summarizing Quant-Wiki content, leveraging QuantMind. A key aspect of this could be generating a Knowledge Graph based on the Quant-Wiki data. Ultimately, we'll aim to provide the corresponding `flow` implementation within the `examples` directory.

@USTCKevinF , would you be able to refine the description for this issue? Please feel free to remove any parts that aren't essential or could be improved.

## 🎯 Motivation

## 📋 Detailed Description

## 🔧 Proposed Implementation

### API Design

```python
# If applicable, show how you envision the API would look
```

### Configuration

```yaml
# If applicable, show any new configuration options
```

## 🎨 User Experience

## 📊 Use Cases

1. **Use Case 1**:
2. **Use Case 2**:
3. **Use Case 3**:

## 🔗 Related Issues

- Relates to #
- Blocks #
- Depends on #

## Implementation Considerations

### Breaking Changes

- [ ] This feature would introduce breaking changes
- [ ] This feature is backward compatible

### Dependencies

- [ ] Requires new dependencies
- [ ] Uses existing dependencies only

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**Checklist**

- [ ] I have searched existing issues to avoid duplicates
- [ ] I have provided a clear and detailed description
- [ ] I have explained the motivation and use cases
- [ ] I have considered the implementation approach
- [ ] I have thought about potential breaking changes