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/api/admin.py

@@ -230,6 +230,30 @@ async def backfill_labels(current_user: User = Depends(get_current_admin)):
     return {"task_id": task.id, "status": "queued"}
 
 
+@router.post("/backfill-cosponsors")
+async def backfill_cosponsors(current_user: User = Depends(get_current_admin)):
+    """Fetch co-sponsor data from Congress.gov for all bills that haven't been fetched yet."""
+    from app.workers.bill_classifier import backfill_all_bill_cosponsors
+    task = backfill_all_bill_cosponsors.delay()
+    return {"task_id": task.id, "status": "queued"}
+
+
+@router.post("/backfill-categories")
+async def backfill_categories(current_user: User = Depends(get_current_admin)):
+    """Classify all bills with text but no category as substantive/commemorative/administrative."""
+    from app.workers.bill_classifier import backfill_bill_categories
+    task = backfill_bill_categories.delay()
+    return {"task_id": task.id, "status": "queued"}
+
+
+@router.post("/calculate-effectiveness")
+async def calculate_effectiveness(current_user: User = Depends(get_current_admin)):
+    """Recalculate member effectiveness scores and percentiles now."""
+    from app.workers.bill_classifier import calculate_effectiveness_scores
+    task = calculate_effectiveness_scores.delay()
+    return {"task_id": task.id, "status": "queued"}
+
+
 @router.post("/resume-analysis")
 async def resume_analysis(current_user: User = Depends(get_current_admin)):
     """Re-queue LLM processing for docs with no brief, and document fetching for bills with no doc."""