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/alembic/versions/0018_add_effectiveness_and_cosponsors.py

@@ -0,0 +1,58 @@
+"""Add bill_category, cosponsors, and member effectiveness score columns
+
+Revision ID: 0018
+Revises: 0017
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "0018"
+down_revision = "0017"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # Bill additions
+    op.add_column("bills", sa.Column("bill_category", sa.String(20), nullable=True))
+    op.add_column("bills", sa.Column("cosponsors_fetched_at", sa.DateTime(timezone=True), nullable=True))
+
+    # Co-sponsors table
+    op.create_table(
+        "bill_cosponsors",
+        sa.Column("id", sa.Integer, primary_key=True, autoincrement=True),
+        sa.Column("bill_id", sa.String, sa.ForeignKey("bills.bill_id", ondelete="CASCADE"), nullable=False),
+        sa.Column("bioguide_id", sa.String, sa.ForeignKey("members.bioguide_id", ondelete="SET NULL"), nullable=True),
+        sa.Column("name", sa.String(200)),
+        sa.Column("party", sa.String(50)),
+        sa.Column("state", sa.String(10)),
+        sa.Column("sponsored_date", sa.Date, nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.text("now()")),
+    )
+    op.create_index("ix_bill_cosponsors_bill_id", "bill_cosponsors", ["bill_id"])
+    op.create_index("ix_bill_cosponsors_bioguide_id", "bill_cosponsors", ["bioguide_id"])
+    # Partial unique index — prevents duplicates for known members, allows multiple nulls
+    op.create_index(
+        "uq_bill_cosponsors_bill_member",
+        "bill_cosponsors",
+        ["bill_id", "bioguide_id"],
+        unique=True,
+        postgresql_where=sa.text("bioguide_id IS NOT NULL"),
+    )
+
+    # Member effectiveness columns
+    op.add_column("members", sa.Column("effectiveness_score", sa.Float, nullable=True))
+    op.add_column("members", sa.Column("effectiveness_percentile", sa.Float, nullable=True))
+    op.add_column("members", sa.Column("effectiveness_tier", sa.String(20), nullable=True))
+
+
+def downgrade():
+    op.drop_column("members", "effectiveness_tier")
+    op.drop_column("members", "effectiveness_percentile")
+    op.drop_column("members", "effectiveness_score")
+    op.drop_index("uq_bill_cosponsors_bill_member", "bill_cosponsors")
+    op.drop_index("ix_bill_cosponsors_bioguide_id", "bill_cosponsors")
+    op.drop_index("ix_bill_cosponsors_bill_id", "bill_cosponsors")
+    op.drop_table("bill_cosponsors")
+    op.drop_column("bills", "cosponsors_fetched_at")
+    op.drop_column("bills", "bill_category")