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/__init__.py

@@ -1,4 +1,5 @@
 from app.models.encounter import Encounter
+from app.models.evolution import Evolution
 from app.models.game import Game
 from app.models.nuzlocke_run import NuzlockeRun
 from app.models.pokemon import Pokemon
@@ -7,6 +8,7 @@ from app.models.route_encounter import RouteEncounter
 
 __all__ = [
     "Encounter",
+    "Evolution",
     "Game",
     "NuzlockeRun",
     "Pokemon",

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}')>"

backend/src/app/models/evolution.py

@@ -0,0 +1,23 @@
+from sqlalchemy import ForeignKey, SmallInteger, String
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.core.database import Base
+
+
+class Evolution(Base):
+    __tablename__ = "evolutions"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    from_pokemon_id: Mapped[int] = mapped_column(ForeignKey("pokemon.id"), index=True)
+    to_pokemon_id: Mapped[int] = mapped_column(ForeignKey("pokemon.id"), index=True)
+    trigger: Mapped[str] = mapped_column(String(30))  # level-up, trade, use-item, etc.
+    min_level: Mapped[int | None] = mapped_column(SmallInteger)
+    item: Mapped[str | None] = mapped_column(String(50))  # e.g. thunder-stone
+    held_item: Mapped[str | None] = mapped_column(String(50))
+    condition: Mapped[str | None] = mapped_column(String(200))  # catch-all for other conditions
+
+    from_pokemon: Mapped["Pokemon"] = relationship(foreign_keys=[from_pokemon_id])
+    to_pokemon: Mapped["Pokemon"] = relationship(foreign_keys=[to_pokemon_id])
+
+    def __repr__(self) -> str:
+        return f"<Evolution(id={self.id}, from={self.from_pokemon_id}, to={self.to_pokemon_id}, trigger='{self.trigger}')>"