fix: shorten alembic revision name and expand version_num column

- Rename 2026_05_27_make_project_id_nullable to 2026_05_27_external_repos
  (33 chars exceeded VARCHAR(32) limit in alembic_version table)
- Add alembic_version column expansion to VARCHAR(64) in migration
- Ensure future migrations won't hit the 32 char limit

apps/api/alembic/versions/2026_05_27_external_repos.py

@@ -1,7 +1,7 @@
 """make_project_id_nullable_in_git_repositories
 
-Revision ID: 2026_05_27_make_project_id_nullable
-Revises: e7adfb4
+Revision ID: 2026_05_27_external_repos
+Revises: 2026_05_26_add_git_mounts
 Create Date: 2026-05-27 08:30:00.000000
 
 """
@@ -12,13 +12,16 @@ import sqlalchemy as sa
 
 
 # revision identifiers, used by Alembic.
-revision: str = "2026_05_27_make_project_id_nullable"
+revision: str = "2026_05_27_external_repos"
 down_revision: Union[str, Sequence[str], None] = "2026_05_26_add_git_mounts"
 branch_labels: Union[str, Sequence[str], None] = None
 depends_on: Union[str, Sequence[str], None] = None
 
 
 def upgrade() -> None:
+    # Expand alembic_version version_num to avoid truncation errors
+    op.execute("ALTER TABLE alembic_version ALTER COLUMN version_num TYPE VARCHAR(64)")
+    
     # Make project_id nullable to allow external repositories
     op.alter_column(
         "git_repositories",
@@ -35,3 +38,4 @@ def downgrade() -> None:
         existing_type=sa.UUID(),
         nullable=False,
     )
+    op.execute("ALTER TABLE alembic_version ALTER COLUMN version_num TYPE VARCHAR(32)")