feat: Member Effectiveness Score + Representation Alignment View (v0.9.9)

Member Effectiveness Score
- New BillCosponsor table (migration 0018) with per-bill co-sponsor
  party data required for the bipartisan multiplier
- bill_category column on Bill (substantive | commemorative | administrative)
  set by a cheap one-shot LLM call after each brief is generated
- effectiveness_score / percentile / tier columns on Member
- New bill_classifier.py worker with 5 tasks:
    classify_bill_category  — triggered from llm_processor after brief
    fetch_bill_cosponsors   — triggered from congress_poller on new bill
    calculate_effectiveness_scores — nightly at 5 AM UTC
    backfill_bill_categories / backfill_all_bill_cosponsors — one-time
- Scoring: distance-traveled pts × bipartisan (1.5×) × substance (0.1×
  for commemorative) × leadership (1.2× for committee chairs)
- Percentile normalised within (seniority tier × party) buckets
- Effectiveness card on member detail page with colour-coded bar
- Admin panel: 3 new backfill/calculate controls in Maintenance section

Representation Alignment View
- New GET /api/alignment endpoint: cross-references user's stanced bill
  follows (pocket_veto/pocket_boost) with followed members' vote positions
- Efficient bulk queries — no N+1 loops
- New /alignment page with ranked member list and alignment bars
- Alignment added to sidebar nav (auth-required)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/models/bill.py

@@ -1,5 +1,5 @@
 from sqlalchemy import (
-    Column, String, Integer, Date, DateTime, Text, ForeignKey, Index
+    Column, String, Integer, Date, DateTime, Text, ForeignKey, Index, UniqueConstraint
 )
 from sqlalchemy.orm import relationship
 from sqlalchemy.sql import func
@@ -26,6 +26,9 @@ class Bill(Base):
     congress_url = Column(String)
     govtrack_url = Column(String)
 
+    bill_category = Column(String(20), nullable=True)  # substantive | commemorative | administrative
+    cosponsors_fetched_at = Column(DateTime(timezone=True))
+
     # Ingestion tracking
     last_checked_at = Column(DateTime(timezone=True))
     actions_fetched_at = Column(DateTime(timezone=True))
@@ -40,6 +43,7 @@ class Bill(Base):
     trend_scores = relationship("TrendScore", back_populates="bill", order_by="desc(TrendScore.score_date)")
     committee_bills = relationship("CommitteeBill", back_populates="bill")
     notes = relationship("BillNote", back_populates="bill", cascade="all, delete-orphan")
+    cosponsors = relationship("BillCosponsor", back_populates="bill", cascade="all, delete-orphan")
 
     __table_args__ = (
         Index("ix_bills_congress_number", "congress_number"),
@@ -87,3 +91,23 @@ class BillDocument(Base):
     __table_args__ = (
         Index("ix_bill_documents_bill_id", "bill_id"),
     )
+
+
+class BillCosponsor(Base):
+    __tablename__ = "bill_cosponsors"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    bill_id = Column(String, ForeignKey("bills.bill_id", ondelete="CASCADE"), nullable=False)
+    bioguide_id = Column(String, ForeignKey("members.bioguide_id", ondelete="SET NULL"), nullable=True)
+    name = Column(String(200))
+    party = Column(String(50))
+    state = Column(String(10))
+    sponsored_date = Column(Date, nullable=True)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    bill = relationship("Bill", back_populates="cosponsors")
+
+    __table_args__ = (
+        Index("ix_bill_cosponsors_bill_id", "bill_id"),
+        Index("ix_bill_cosponsors_bioguide_id", "bioguide_id"),
+    )