Separate PokeAPI ID from national dex for correct form identification

Pokemon forms (e.g., Alolan Rattata) had their PokeAPI ID (10091) stored as
national_dex, causing them to display incorrectly. This renames the unique
identifier to pokeapi_id and adds a real national_dex field shared between
forms and their base species, so Alolan Rattata correctly shows as #19.

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

backend/src/app/schemas/pokemon.py

@@ -5,6 +5,7 @@ from app.schemas.base import CamelModel
 
 class PokemonResponse(CamelModel):
     id: int
+    pokeapi_id: int
     national_dex: int
     name: str
     types: list[str]
@@ -47,6 +48,7 @@ class RouteEncounterDetailResponse(RouteEncounterResponse):
 
 
 class PokemonCreate(CamelModel):
+    pokeapi_id: int
     national_dex: int
     name: str
     types: list[str]
@@ -54,6 +56,7 @@ class PokemonCreate(CamelModel):
 
 
 class PokemonUpdate(CamelModel):
+    pokeapi_id: int | None = None
     national_dex: int | None = None
     name: str | None = None
     types: list[str] | None = None
@@ -76,6 +79,7 @@ class RouteEncounterUpdate(CamelModel):
 
 
 class BulkImportItem(BaseModel):
+    pokeapi_id: int
     national_dex: int
     name: str
     types: list[str]