fix: correct migration chain for league settings columns (2.5.1)

Migration 0003_league_settings was chained to 0002 but the DB was already
at 0003_site_admin (an applied migration with no version file). Added a stub
for 0003_site_admin to satisfy the chain and updated the down_revision on
0003_league_settings accordingly. Columns eligible_min_sessions and
break_even_cents now apply cleanly on top of the existing schema.

migrations/versions/0003_league_settings.py

@@ -11,7 +11,7 @@ import sqlalchemy as sa
 
 
 revision = "0003_league_settings"
-down_revision = "0002_league_public_key"
+down_revision = "0003_site_admin"
 branch_labels = None
 depends_on = None
 

migrations/versions/0003_site_admin.py

@@ -0,0 +1,23 @@
+"""site admin (stub — already applied)
+
+Revision ID: 0003_site_admin
+Revises: 0002_league_public_key
+Create Date: 2026-06-26
+"""
+from __future__ import annotations
+
+from alembic import op
+
+
+revision = "0003_site_admin"
+down_revision = "0002_league_public_key"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    pass
+
+
+def downgrade() -> None:
+    pass