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/alembic/versions/e5f6a7b8c9d0_rename_national_dex_add_pokeapi_id.py

@@ -0,0 +1,53 @@
+"""rename national_dex to pokeapi_id, add real national_dex
+
+Revision ID: e5f6a7b8c9d0
+Revises: d4e5f6a7b8c9
+Create Date: 2026-02-07 10:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'e5f6a7b8c9d0'
+down_revision: Union[str, Sequence[str], None] = 'd4e5f6a7b8c9'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Rename national_dex -> pokeapi_id and widen to Integer
+    op.alter_column(
+        'pokemon', 'national_dex',
+        new_column_name='pokeapi_id',
+        type_=sa.Integer(),
+        existing_type=sa.SmallInteger(),
+        existing_nullable=False,
+    )
+
+    # Add real national_dex column (shared between forms and base species)
+    op.add_column(
+        'pokemon',
+        sa.Column('national_dex', sa.SmallInteger(), nullable=False, server_default='0'),
+    )
+
+    # Populate national_dex = pokeapi_id for all existing rows
+    # (correct for base species; forms will be fixed by re-seeding)
+    op.execute('UPDATE pokemon SET national_dex = pokeapi_id')
+
+    # Remove the default now that all rows are populated
+    op.alter_column('pokemon', 'national_dex', server_default=None)
+
+
+def downgrade() -> None:
+    op.drop_column('pokemon', 'national_dex')
+    op.alter_column(
+        'pokemon', 'pokeapi_id',
+        new_column_name='national_dex',
+        type_=sa.SmallInteger(),
+        existing_type=sa.Integer(),
+        existing_nullable=False,
+    )