fix: use boolean literal for reversible server_default

PostgreSQL rejects DEFAULT 1 for boolean columns; use DEFAULT true
which works on both PostgreSQL and SQLite (3.23.0+).

alembic/versions/20260713_0100_f1e2d3c4b5a6_add_reversible_to_routes.py

@@ -28,7 +28,7 @@ def upgrade() -> None:
             "reversible",
             sa.Boolean(),
             nullable=False,
-            server_default=sa.text("1"),
+            server_default=sa.text("true"),
         ),
     )