Add pokemon evolution support across the full stack

- Evolution model with trigger, level, item, and condition fields
- Encounter.current_pokemon_id tracks evolved species separately
- Alembic migration for evolutions table and current_pokemon_id column
- Seed pipeline loads evolution data with manual overrides
- GET /pokemon/{id}/evolutions and PATCH /encounters/{id} endpoints
- Evolve button in StatusChangeModal with evolution method details
- PokemonCard shows evolved species with "Originally" label

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

backend/src/app/models/encounter.py

@@ -18,13 +18,21 @@ class Encounter(Base):
     catch_level: Mapped[int | None] = mapped_column(SmallInteger)
     faint_level: Mapped[int | None] = mapped_column(SmallInteger)
     death_cause: Mapped[str | None] = mapped_column(String(100))
+    current_pokemon_id: Mapped[int | None] = mapped_column(
+        ForeignKey("pokemon.id"), index=True
+    )
     caught_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), server_default=func.now()
     )
 
     run: Mapped["NuzlockeRun"] = relationship(back_populates="encounters")
     route: Mapped["Route"] = relationship(back_populates="encounters")
-    pokemon: Mapped["Pokemon"] = relationship(back_populates="encounters")
+    pokemon: Mapped["Pokemon"] = relationship(
+        foreign_keys=[pokemon_id], back_populates="encounters"
+    )
+    current_pokemon: Mapped["Pokemon | None"] = relationship(
+        foreign_keys=[current_pokemon_id]
+    )
 
     def __repr__(self) -> str:
         return f"<Encounter(id={self.id}, pokemon_id={self.pokemon_id}, status='{self.status}')>"