Move Studio team member filtering out of host layer

[louis4li]

Problem

StudioTeamEndpoints.HandleListMembersAsync currently validates the team, pages through members, filters by TeamId in memory, and synthesizes pagination in the Host/API layer. This puts business query orchestration in the host and does not push team_id filtering into the projection store.

Why it matters

Host endpoints should compose HTTP concerns only. Team-member listing is an application/query-port concern and should be backed by projection-store filtering.

Acceptance criteria

• Application/query port exposes a typed contract for listing members by team.
• Projection query port pushes scope_id/team_id filters into the document store.
• Host endpoint delegates to the application/query contract without in-memory pagination/filter orchestration.
• Tests cover filtering and pagination at the query-port/application boundary.

Source

Follow-up from StudioMember async bind PR review; out of scope for the binding-run PR.