Fix: preserve document fields during Gotenberg conversion (#13271)

Gotenberg's LibreOffice route enables updateIndexes by default, which refreshes dynamic fields (e.g. auto-dates) to the current date. Disable it so field values are preserved as authored.

src/paperless/tests/parsers/test_tika_parser.py

@@ -223,4 +223,11 @@ class TestTikaParser:
 
         assert form_field_found
 
+        # Field updates must be disabled so LibreOffice preserves document
+        # fields (e.g. auto-date fields) as authored rather than refreshing
+        # them to the current date.
+        assert any(
+            b'name="updateIndexes"' in part and b"false" in part for part in parts
+        )
+
         httpx_mock.reset()