[Feature] Scholar network and trend visualization UI

[jerry609]

Source TODO

• 前端：学者关系图可视化
• 前端：学者趋势图表

Scope

• ScholarNetworkGraph.tsx
• ScholarTrendsChart.tsx
• Integrate with existing /scholar/network|trends APIs

Acceptance Criteria

• Interactive graph + trend charts are stable with 10-200 nodes

[jerry609]

Implemented in commit 31b0aeb on branch feat/dailypaper-sse-stream: added ScholarNetworkGraph + ScholarTrendsChart components and integrated them into /scholars/[id] with real scholar network/trend API data.