feat(web): wire up MCP task support — Tasks screen, Run-as-task, status toasts (#1422) (#1424)

Wires the ported Tasks screen + core task subsystem through App.tsx: sticky Clear Completed, cancel/refresh error toasts, core-side per-task progress correlation, Run-as-task on the Tools screen (gated on server support), per-server Task TTL, and live task-status toasts.

clients/web/src/components/groups/ServerSettingsModal/ServerSettingsModal.tsx

@@ -83,7 +83,7 @@ export function ServerSettingsModal({
   }
 
   function handleTimeoutChange(
-    field: "connectionTimeout" | "requestTimeout",
+    field: "connectionTimeout" | "requestTimeout" | "taskTtl",
     value: number,
   ) {
     onSettingsChange({ ...settings, [field]: value });