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/models/member_interest.py

@@ -0,0 +1,47 @@
+from sqlalchemy import Column, Integer, String, Date, Float, Text, DateTime, ForeignKey, Index, UniqueConstraint
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class MemberTrendScore(Base):
+    __tablename__ = "member_trend_scores"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    member_id = Column(String, ForeignKey("members.bioguide_id", ondelete="CASCADE"), nullable=False)
+    score_date = Column(Date, nullable=False)
+    newsapi_count = Column(Integer, default=0)
+    gnews_count = Column(Integer, default=0)
+    gtrends_score = Column(Float, default=0.0)
+    composite_score = Column(Float, default=0.0)
+
+    member = relationship("Member", back_populates="trend_scores")
+
+    __table_args__ = (
+        UniqueConstraint("member_id", "score_date", name="uq_member_trend_scores_member_date"),
+        Index("ix_member_trend_scores_member_id", "member_id"),
+        Index("ix_member_trend_scores_score_date", "score_date"),
+        Index("ix_member_trend_scores_composite", "composite_score"),
+    )
+
+
+class MemberNewsArticle(Base):
+    __tablename__ = "member_news_articles"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    member_id = Column(String, ForeignKey("members.bioguide_id", ondelete="CASCADE"), nullable=False)
+    source = Column(String(200))
+    headline = Column(Text)
+    url = Column(String)
+    published_at = Column(DateTime(timezone=True))
+    relevance_score = Column(Float, default=0.0)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    member = relationship("Member", back_populates="news_articles")
+
+    __table_args__ = (
+        UniqueConstraint("member_id", "url", name="uq_member_news_member_url"),
+        Index("ix_member_news_articles_member_id", "member_id"),
+        Index("ix_member_news_articles_published_at", "published_at"),
+    )