fix: add retry logic for ETag conflicts in category change test

The test_attachments_category_change_handling test was failing in CI with
HTTP 412 Precondition Failed errors. This is caused by the background vector
scanner (runs every 10 seconds) modifying notes between when the test fetches
the ETag and when it attempts to update the category.

Solution: Added retry logic (up to 3 attempts) that refetches the latest ETag
and retries the update operation when encountering 412 errors. This handles
the race condition gracefully while still catching genuine errors.

tests/client/notes/test_attachments.py

@@ -239,23 +239,46 @@ async def test_attachments_category_change_handling(nc_client: NextcloudClient):
         assert retrieved_content1 == attachment_content
         logger.info("Attachment retrieved successfully from initial category.")
 
-        # 4. Update note category
+        # 4. Update note category (with retry for ETag conflicts from background scanner)
         logger.info(
             f"Updating note {note_id} category from '{initial_category}' to '{new_category}'"
         )
-        # Need to fetch the latest etag after attachment add (WebDAV ops don't update note etag)
-        current_note_data = await nc_client.notes.get_note(note_id=note_id)
-        current_etag = current_note_data["etag"]
-        updated_note = await nc_client.notes.update(
-            note_id=note_id,
-            etag=current_etag,
-            category=new_category,
-            title=note_title,
-            content="Updated content",  # Pass required fields
-        )
-        etag3 = updated_note["etag"]
-        assert updated_note["category"] == new_category
-        logger.info(f"Note category updated successfully. New Etag: {etag3}")
+        # Retry logic for 412 Precondition Failed (ETag conflict)
+        # This can happen if the background vector scanner touches the note
+        max_update_attempts = 3
+        for attempt in range(max_update_attempts):
+            try:
+                # Fetch the latest etag
+                current_note_data = await nc_client.notes.get_note(note_id=note_id)
+                current_etag = current_note_data["etag"]
+                logger.info(
+                    f"Update attempt {attempt + 1}/{max_update_attempts}, current etag: {current_etag}"
+                )
+
+                updated_note = await nc_client.notes.update(
+                    note_id=note_id,
+                    etag=current_etag,
+                    category=new_category,
+                    title=note_title,
+                    content="Updated content",  # Pass required fields
+                )
+                etag3 = updated_note["etag"]
+                assert updated_note["category"] == new_category
+                logger.info(f"Note category updated successfully. New Etag: {etag3}")
+                break  # Success, exit retry loop
+
+            except HTTPStatusError as e:
+                if e.response.status_code == 412 and attempt < max_update_attempts - 1:
+                    # ETag conflict (likely from background scanner), retry
+                    logger.warning(
+                        f"ETag conflict (412) on attempt {attempt + 1}, retrying..."
+                    )
+                    time.sleep(1)  # Brief delay before retry
+                    continue
+                else:
+                    # Not a 412 or out of retries, re-raise
+                    raise
+
         time.sleep(1)
 
         # 5. Verify attachment retrieval from *new* category (passing new category)