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.

config.py

@@ -9,7 +9,7 @@ DATA_PATH = BASE_DIR / "data" / "entries.csv"
 DEFAULT_DATABASE_URL = f"sqlite:///{BASE_DIR / 'data' / 'boker-dev.sqlite3'}"
 
 ELIGIBLE_MIN_SESSIONS = 3
-APP_VERSION = "2.5.0"
+APP_VERSION = "2.5.1"
 
 
 def load_local_env(env_path: Path) -> None: