feat: roll-call votes + granular alert filter fix (v0.9.5)

Roll-call votes:
- Migration 0017: bill_votes + member_vote_positions tables
- Fetch vote XML directly from House Clerk / Senate LIS URLs
  embedded in bill actions recordedVotes objects
- GET /api/bills/{id}/votes triggers background fetch on first view
- VotePanel on bill detail: yea/nay bar, result badge, followed
  member positions with Sen./Rep. title, party badge, and state

Alert filter fix:
- _should_dispatch returns True when alert_filters is None so users
  who haven't saved filters still receive all notifications

Authored-By: Jack Levy

backend/app/services/congress_api.py

@@ -90,6 +90,11 @@ def get_bill_text_versions(congress: int, bill_type: str, bill_number: int) -> d
     return _get(f"/bill/{congress}/{bill_type.lower()}/{bill_number}/text", {})
 
 
+def get_vote_detail(congress: int, chamber: str, session: int, roll_number: int) -> dict:
+    chamber_slug = "house" if chamber.lower() == "house" else "senate"
+    return _get(f"/vote/{congress}/{chamber_slug}/{session}/{roll_number}", {})
+
+
 def get_members(offset: int = 0, limit: int = 250, current_member: bool = True) -> dict:
     params: dict = {"offset": offset, "limit": limit}
     if current_member: