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/schemas/schemas.py

@@ -8,8 +8,12 @@ from pydantic import BaseModel
 
 class NotificationSettingsResponse(BaseModel):
     ntfy_topic_url: str = ""
+    ntfy_auth_method: str = "none"  # none | token | basic
     ntfy_token: str = ""
+    ntfy_username: str = ""
+    ntfy_password: str = ""
     ntfy_enabled: bool = False
+    rss_enabled: bool = False
     rss_token: Optional[str] = None
 
     model_config = {"from_attributes": True}
@@ -17,8 +21,12 @@ class NotificationSettingsResponse(BaseModel):
 
 class NotificationSettingsUpdate(BaseModel):
     ntfy_topic_url: Optional[str] = None
+    ntfy_auth_method: Optional[str] = None
     ntfy_token: Optional[str] = None
+    ntfy_username: Optional[str] = None
+    ntfy_password: Optional[str] = None
     ntfy_enabled: Optional[bool] = None
+    rss_enabled: Optional[bool] = None
 
 T = TypeVar("T")