fix

backend/env/database.py

@@ -476,6 +476,17 @@ def _execute_sqlite(sql: str) -> tuple[list[dict], str | None]:
         conn.close()
 
 
+def _pg_safe(v: object) -> object:
+    """Convert PostgreSQL-specific types to JSON-serializable equivalents."""
+    from decimal import Decimal
+    import datetime
+    if isinstance(v, Decimal):
+        return float(v)
+    if isinstance(v, (datetime.date, datetime.datetime, datetime.time)):
+        return v.isoformat()
+    return v
+
+
 def _execute_postgres(sql: str) -> tuple[list[dict], str | None]:
     import psycopg2  # type: ignore[import]
     import psycopg2.extras  # type: ignore[import]
@@ -484,7 +495,7 @@ def _execute_postgres(sql: str) -> tuple[list[dict], str | None]:
         cur = conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor)
         cur.execute(sql)
         if cur.description is not None:
-            rows = [dict(row) for row in cur.fetchall()]
+            rows = [{k: _pg_safe(v) for k, v in dict(row).items()} for row in cur.fetchall()]
         else:
             rows = []
         conn.commit()