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/schemas/encounter.py

@@ -18,6 +18,7 @@ class EncounterUpdate(CamelModel):
     status: str | None = None
     faint_level: int | None = None
     death_cause: str | None = None
+    current_pokemon_id: int | None = None
 
 
 class EncounterResponse(CamelModel):
@@ -25,6 +26,7 @@ class EncounterResponse(CamelModel):
     run_id: int
     route_id: int
     pokemon_id: int
+    current_pokemon_id: int | None
     nickname: str | None
     status: str
     catch_level: int | None
@@ -35,4 +37,5 @@ class EncounterResponse(CamelModel):
 
 class EncounterDetailResponse(EncounterResponse):
     pokemon: PokemonResponse
+    current_pokemon: PokemonResponse | None
     route: RouteResponse