Fix alembic revision IDs to match existing naming convention

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

blog/alembic/versions/0004_ghost_id_nullable_and_defaults.py

@@ -6,8 +6,8 @@ Revises: 0003_add_page_configs
 from alembic import op
 import sqlalchemy as sa
 
-revision = "0004"
-down_revision = "0003_add_page_configs"
+revision = "blog_0004"
+down_revision = "blog_0003"
 branch_labels = None
 depends_on = None