fix: pass web search results to model when embedding & retrieval enabled (#25600)

Web search results stored as a vector collection were silently dropped
before retrieval when BYPASS_RETRIEVAL_ACCESS_CONTROL is False (the
default). The server-generated web_search file item carries a
'collection_name' but its 'web_search' type is not matched by any
explicit dispatch branch in get_sources_from_items, so it fell through
to the untrusted client-supplied collection_name branch and was ignored.

Add an explicit branch for type == 'web_search' items so the collection
is queried again. Access control is preserved: the collection still
passes through filter_accessible_collections, which already allowlists
web-search-* and bypasses only for admins.

Regression introduced when the retrieval access-control hardening gated
the bare collection_name fallback behind BYPASS_RETRIEVAL_ACCESS_CONTROL.

backend/open_webui/retrieval/utils.py

@@ -1548,6 +1548,10 @@ async def get_sources_from_items(
                 'documents': [[doc.get('content') for doc in item.get('docs')]],
                 'metadatas': [[doc.get('metadata') for doc in item.get('docs')]],
             }
+        elif item.get('type') == 'web_search' and item.get('collection_name'):
+            # Trusted server-generated collection; authorized by
+            # filter_accessible_collections below (allowlists web-search-*).
+            collection_names.append(item['collection_name'])
         elif item.get('collection_name'):
             if BYPASS_RETRIEVAL_ACCESS_CONTROL:
                 collection_names.append(item['collection_name'])