feat: Add configurable DDGS backend selection with UI support (#20366)

* init

* Update WebSearch.svelte

* reorder

backend/open_webui/retrieval/web/duckduckgo.py

@@ -13,12 +13,14 @@ def search_duckduckgo(
     count: int,
     filter_list: Optional[list[str]] = None,
     concurrent_requests: Optional[int] = None,
+    backend: Optional[str] = "auto",
 ) -> list[SearchResult]:
     """
     Search using DuckDuckGo's Search API and return the results as a list of SearchResult objects.
     Args:
         query (str): The query to search for
         count (int): The number of results to return
+        backend (str): The search backend to use (auto, duckduckgo, google, brave, etc.)
 
     Returns:
         list[SearchResult]: A list of search results
@@ -32,7 +34,7 @@ def search_duckduckgo(
         # Use the ddgs.text() method to perform the search
         try:
             search_results = ddgs.text(
-                query, safesearch="moderate", max_results=count, backend="lite"
+                query, safesearch="moderate", max_results=count, backend=backend
             )
         except RatelimitException as e:
             log.error(f"RatelimitException: {e}")