feat: per-user notifications (ntfy + RSS), deduplicated actions, backfill task

Notifications:
- New /notifications page accessible to all users (ntfy + RSS config)
- ntfy now supports no-auth, Bearer token, and HTTP Basic auth (for ACL-protected self-hosted servers)
- RSS enabled/disabled independently of ntfy; token auto-generated on first GET
- Notification settings removed from admin-only Settings page; replaced with link card
- Sidebar adds Notifications nav link for all users
- notification_dispatcher.py: fan-out now marks RSS events dispatched independently

Action history:
- Migration 0012: deduplicates existing bill_actions rows and adds UNIQUE(bill_id, action_date, action_text)
- congress_poller.py: replaces existence-check inserts with ON CONFLICT DO NOTHING (race-condition safe)
- Added backfill_all_bill_actions task (no date filter) + admin endpoint POST /backfill-all-actions

Authored-By: Jack Levy

backend/app/models/__init__.py

@@ -4,6 +4,7 @@ from app.models.follow import Follow
 from app.models.member import Member
 from app.models.member_interest import MemberTrendScore, MemberNewsArticle
 from app.models.news import NewsArticle
+from app.models.notification import NotificationEvent
 from app.models.setting import AppSetting
 from app.models.trend import TrendScore
 from app.models.committee import Committee, CommitteeBill
@@ -19,6 +20,7 @@ __all__ = [
     "MemberTrendScore",
     "MemberNewsArticle",
     "NewsArticle",
+    "NotificationEvent",
     "AppSetting",
     "TrendScore",
     "Committee",

backend/app/models/notification.py

@@ -0,0 +1,27 @@
+from sqlalchemy import Column, DateTime, ForeignKey, Index, Integer, String
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class NotificationEvent(Base):
+    __tablename__ = "notification_events"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    bill_id = Column(String, ForeignKey("bills.bill_id", ondelete="CASCADE"), nullable=False)
+    # new_document | new_amendment | bill_updated
+    event_type = Column(String(50), nullable=False)
+    # {bill_title, bill_label, brief_summary, bill_url}
+    payload = Column(JSONB)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    dispatched_at = Column(DateTime(timezone=True), nullable=True)
+
+    user = relationship("User", back_populates="notification_events")
+
+    __table_args__ = (
+        Index("ix_notification_events_user_id", "user_id"),
+        Index("ix_notification_events_dispatched_at", "dispatched_at"),
+    )

backend/app/models/user.py

@@ -14,6 +14,8 @@ class User(Base):
     hashed_password = Column(String, nullable=False)
     is_admin = Column(Boolean, nullable=False, default=False)
     notification_prefs = Column(JSONB, nullable=False, default=dict)
+    rss_token = Column(String, unique=True, nullable=True, index=True)
     created_at = Column(DateTime(timezone=True), server_default=func.now())
 
     follows = relationship("Follow", back_populates="user", cascade="all, delete-orphan")
+    notification_events = relationship("NotificationEvent", back_populates="user", cascade="all, delete-orphan")