feat: bill action pipeline, What Changed UI, citation backfill, admin panel

Backend:
- Add fetch_bill_actions task with pagination and idempotent upsert
- Add fetch_actions_for_active_bills nightly batch (4 AM UTC beat schedule)
- Wire fetch_bill_actions into new-bill creation and _update_bill_if_changed
- Add backfill_brief_citations task: detects pre-citation briefs by JSONB
  type check, deletes them, re-queues LLM processing against stored text
  (LLM calls only — zero Congress.gov or GovInfo calls)
- Add admin endpoints: POST /bills/{id}/reprocess, /backfill-citations,
  /trigger-fetch-actions; add uncited_briefs count to /stats

Frontend:
- New BriefPanel component: wraps AIBriefCard, adds amber "What Changed"
  badge for amendment briefs and collapsible version history with
  inline brief expansion
- Swap AIBriefCard for BriefPanel on bill detail page
- Admin panel: Backfill Citations + Fetch Bill Actions buttons; amber
  warning in stats when uncited briefs remain
- Add feature roadmap document with phased plan through Phase 5

Co-Authored-By: Jack Levy

backend/app/workers/congress_poller.py

@@ -6,8 +6,11 @@ Uses fromDateTime to fetch only recently updated bills.
 All operations are idempotent.
 """
 import logging
+import time
 from datetime import datetime, timedelta, timezone
 
+from sqlalchemy import or_
+
 from app.database import get_sync_db
 from app.models import Bill, BillAction, Member, AppSetting
 from app.services import congress_api
@@ -84,9 +87,10 @@ def poll_congress_bills(self):
                     db.add(Bill(**parsed))
                     db.commit()
                     new_count += 1
-                    # Enqueue document fetch
+                    # Enqueue document and action fetches
                     from app.workers.document_fetcher import fetch_bill_documents
                     fetch_bill_documents.delay(bill_id)
+                    fetch_bill_actions.delay(bill_id)
                 else:
                     _update_bill_if_changed(db, existing, parsed)
                     updated_count += 1
@@ -198,6 +202,101 @@ def backfill_sponsor_ids(self):
         db.close()
 
 
+@celery_app.task(bind=True, max_retries=3, name="app.workers.congress_poller.fetch_bill_actions")
+def fetch_bill_actions(self, bill_id: str):
+    """Fetch and sync all actions for a bill from Congress.gov. Idempotent."""
+    db = get_sync_db()
+    try:
+        bill = db.get(Bill, bill_id)
+        if not bill:
+            logger.warning(f"fetch_bill_actions: bill {bill_id} not found")
+            return
+
+        offset = 0
+        inserted = 0
+        while True:
+            try:
+                response = congress_api.get_bill_actions(
+                    bill.congress_number, bill.bill_type, bill.bill_number, offset=offset
+                )
+            except Exception as exc:
+                raise self.retry(exc=exc, countdown=60)
+
+            actions_data = response.get("actions", [])
+            if not actions_data:
+                break
+
+            for action in actions_data:
+                action_date_str = action.get("actionDate")
+                action_text = action.get("text", "")
+                action_type = action.get("type")
+                chamber = action.get("chamber")
+
+                # Idempotency check: skip if (bill_id, action_date, action_text) exists
+                exists = (
+                    db.query(BillAction)
+                    .filter(
+                        BillAction.bill_id == bill_id,
+                        BillAction.action_date == action_date_str,
+                        BillAction.action_text == action_text,
+                    )
+                    .first()
+                )
+                if not exists:
+                    db.add(BillAction(
+                        bill_id=bill_id,
+                        action_date=action_date_str,
+                        action_text=action_text,
+                        action_type=action_type,
+                        chamber=chamber,
+                    ))
+                    inserted += 1
+
+            db.commit()
+            offset += 250
+            if len(actions_data) < 250:
+                break
+
+        bill.actions_fetched_at = datetime.now(timezone.utc)
+        db.commit()
+        logger.info(f"fetch_bill_actions: {bill_id} — inserted {inserted} new actions")
+        return {"bill_id": bill_id, "inserted": inserted}
+    except Exception as exc:
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+
+@celery_app.task(bind=True, name="app.workers.congress_poller.fetch_actions_for_active_bills")
+def fetch_actions_for_active_bills(self):
+    """Nightly batch: enqueue action fetches for recently active bills missing action data."""
+    db = get_sync_db()
+    try:
+        cutoff = datetime.now(timezone.utc).date() - timedelta(days=30)
+        bills = (
+            db.query(Bill)
+            .filter(
+                Bill.latest_action_date >= cutoff,
+                or_(
+                    Bill.actions_fetched_at.is_(None),
+                    Bill.latest_action_date > Bill.actions_fetched_at,
+                ),
+            )
+            .limit(200)
+            .all()
+        )
+        queued = 0
+        for bill in bills:
+            fetch_bill_actions.delay(bill.bill_id)
+            queued += 1
+            time.sleep(0.2)  # ~5 tasks/sec to avoid Redis burst
+        logger.info(f"fetch_actions_for_active_bills: queued {queued} bills")
+        return {"queued": queued}
+    finally:
+        db.close()
+
+
 def _update_bill_if_changed(db, existing: Bill, parsed: dict) -> bool:
     """Update bill fields if anything has changed. Returns True if updated."""
     changed = False
@@ -210,7 +309,8 @@ def _update_bill_if_changed(db, existing: Bill, parsed: dict) -> bool:
     if changed:
         existing.last_checked_at = datetime.now(timezone.utc)
         db.commit()
-        # Check for new text versions now that the bill has changed
+        # Check for new text versions and sync actions now that the bill has changed
         from app.workers.document_fetcher import fetch_bill_documents
         fetch_bill_documents.delay(existing.bill_id)
+        fetch_bill_actions.delay(existing.bill_id)
     return changed