Add Hall of Fame team selection for completed runs

After marking a run as completed, a modal prompts the player to select
which Pokemon (up to 6) entered the Hall of Fame. The selection is stored
as hof_encounter_ids on the run, displayed in the victory banner, and
can be edited later. This lays the foundation for scoping genlocke
retireHoF to only the actual HoF team.

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

backend/src/app/models/nuzlocke_run.py

@@ -19,6 +19,7 @@ class NuzlockeRun(Base):
         DateTime(timezone=True), server_default=func.now()
     )
     completed_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    hof_encounter_ids: Mapped[list[int] | None] = mapped_column(JSONB, default=None)
 
     game: Mapped["Game"] = relationship(back_populates="runs")
     encounters: Mapped[list["Encounter"]] = relationship(back_populates="run")