Restrict transfers to HoF team and prevent blocking starter route

Transfer modal now only appears when a Hall of Fame team is selected,
using the existing hofTeam data instead of the survivors endpoint.
Without a HoF selection, advance proceeds directly with no transfer step.

Transferred encounters are now a separate category: they appear in their
own "Transferred Pokemon" section, don't occupy route slots in the
encounter map, and don't block the route-lock check (excluded via
genlocke_transfers subquery). The run detail endpoint returns
transferEncounterIds so the frontend can distinguish them.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/app/schemas/run.py

@@ -42,3 +42,4 @@ class RunDetailResponse(RunResponse):
     game: GameResponse
     encounters: list[EncounterDetailResponse] = []
     genlocke: RunGenlockeContext | None = None
+    transfer_encounter_ids: list[int] = []