修复迁移幂等并补部署检查

backend/tests/test_migration_safety.py

@@ -0,0 +1,17 @@
+from pathlib import Path
+
+
+def test_is_locked_migration_is_idempotent():
+    source = Path("alembic/versions/20260116_01_add_is_locked_to_studies.py").read_text(encoding="utf-8")
+
+    assert 'if "is_locked" not in columns:' in source
+    assert 'if "is_locked" in columns:' in source
+
+
+def test_migration_state_check_script_exists():
+    source = Path("scripts/check_migration_state.py").read_text(encoding="utf-8")
+
+    assert "missing alembic_version table" in source
+    assert "studies" in source
+    assert "subjects" in source
+    assert "monitoring_visit_issues" in source