perf: build info log messages lazily so raising the log level actually saves work (#27837)

Raising GLOBAL_LOG_LEVEL to WARNING buys quieter output but not less work: 241 INFO call sites interpolate their payload into an f-string before the logging call gets to drop it. The heaviest is get_doc, which logs every chunk id and metadata dict in a collection, so on the full-context retrieval path that is the entire knowledge base, once per chat request.

That one line at WARNING, CPython 3.12:

| knowledge base | payload | before   | after   |
| -------------- | ------- | -------- | ------- |
| top-k of 3     | 1.2 kB  | 3.8 us   | 0.07 us |
| 500 chunks     | 201 kB  | 583.6 us | 0.08 us |
| 5000 chunks    | 2.0 MB  | 5.8 ms   | 0.15 us |

The lazy form log.info('query_doc:result %s %s', result.ids, result.metadatas) hands the payload to record.getMessage(), which the InterceptHandler only reaches once a record has passed the level check. Output at INFO is byte-identical. Two sites that already built their message eagerly, one str concat and one % operator, move to the same lazy form.

backend/open_webui/retrieval/web/exa.py

@@ -31,7 +31,7 @@ def search_exa(
         count (int): Number of results to return
         filter_list (Optional[list[str]]): List of domains to filter results by
     """
-    log.info(f'Searching with Exa for query: {query}')
+    log.info('Searching with Exa for query: %s', query)
 
     headers = {'Authorization': f'Bearer {api_key}', 'Content-Type': 'application/json'}
 
@@ -58,7 +58,7 @@ def search_exa(
                 )
             )
 
-        log.info(f'Found {len(results)} results')
+        log.info('Found %s results', len(results))
         return [
             SearchResult(
                 link=result.url,