[Feature] Trending papers API and page

[jerry609]

Source TODO

• Trending 评分公式
• GET /api/research/trending
• 前端 Trending 页面

Scope

• Implement trending score blend and endpoint
• Add frontend page with filters

Acceptance Criteria

• Trending list updates over time and is explainable

[jerry609]

Implemented in commit 90f6880 on branch feat/dailypaper-sse-stream: explainable trending score service, /api/research/trending endpoint, proxy + /trending UI page with filters and score breakdown.