Scope politician voting frames to the viewed meeting

Large-roster Chrome testing with concurrent ongoing meetings reproduced cross-meeting voting presentation. Current holders Fetter Anton and Svarteper in meeting 15 were routed to another ongoing case; Tussi’s meeting-15 page displayed the unrelated `E2E-prospektiv` poll from meeting 17. Onkel Skrue was an eligible active holder/non-voter in meeting 17 but `/politician/meetings` remained bound to unrelated case 7/2026 and never exposed meeting 17’s ballot. The politician layout and voting-frame endpoints render `current_user.current_meeting`, which selects one latest ongoing meeting, even when the user is viewing another authorized meeting. Scope the voting frame, streams, current role, and ballot to the explicit meeting context; when multiple meetings are ongoing, provide deterministic selection/navigation without leaking another meeting’s poll into the page. Verify displaced and unavailable users still receive no ballot.