perf: optimize backend — HTTP client, DB queries, error handling, and config cleanup

src/hooks/use-connections.ts

@@ -103,7 +103,9 @@ export function useReconnect() {
       setPgVersion(version);
       setDbFlavor(id, flavor);
       setCurrentDatabase(database);
-      queryClient.invalidateQueries();
+      queryClient.invalidateQueries({ queryKey: ["databases"] });
+      queryClient.invalidateQueries({ queryKey: ["schemas"] });
+      queryClient.invalidateQueries({ queryKey: ["completion-schema"] });
     },
   });
 }