feat(interest): add public interest tracking for members of Congress

Adds Google Trends, NewsAPI, and Google News RSS scoring for members,
mirroring the existing bill interest pipeline. Member profiles now show
a Public Interest chart (with signal breakdown) and a Related News panel.

Key changes:
- New member_trend_scores + member_news_articles tables (migration 0008)
- fetch_gnews_articles() added to news_service for unlimited RSS article storage
- Bill news fetcher now combines NewsAPI + Google News RSS (more coverage)
- New member_interest Celery worker with scheduled news + trend tasks
- GET /members/{id}/trend and /news API endpoints
- TrendChart redesigned with signal breakdown badges and bar+line combo chart
- NewsPanel accepts generic article shape (bills and members)

Co-Authored-By: Jack Levy

backend/app/services/trends_service.py

@@ -50,6 +50,14 @@ def get_trends_score(keywords: list[str]) -> float:
         return 0.0
 
 
+def keywords_for_member(first_name: str, last_name: str) -> list[str]:
+    """Extract meaningful search keywords for a member of Congress."""
+    full_name = f"{first_name} {last_name}".strip()
+    if not full_name:
+        return []
+    return [full_name]
+
+
 def keywords_for_bill(title: str, short_title: str, topic_tags: list[str]) -> list[str]:
     """Extract meaningful search keywords for a bill."""
     keywords = []