test(realestate): truncate tables for isolation instead of file delete

Replace os.remove() in conftest autouse fixture with per-table DELETE
to avoid Windows SQLite file-lock PermissionError being swallowed
silently and leaking state across tests. Remove the inline DELETE
workaround from test_profile_api.py that was coupling the test to
internal DB knowledge.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

realestate-lab/tests/test_profile_api.py

@@ -26,11 +26,7 @@ def test_profile_update_accepts_new_fields():
 
 def test_profile_get_returns_defaults_for_new_fields():
     from app.main import app
-    from app.db import upsert_profile, _conn
-
-    # 이전 테스트 데이터 제거 후 새 프로필 삽입
-    with _conn() as conn:
-        conn.execute("DELETE FROM user_profile")
+    from app.db import upsert_profile
     upsert_profile({"name": "기본"})
 
     with TestClient(app) as client: