fix(proxy): resolve system proxy toggle stuck and state desync (#6614) (#6657)

* fix(proxy): resolve system proxy toggle stuck and state desync (#6614)

Backend: replace hand-rolled AtomicBool lock in update_sysproxy() with
tokio::sync::Mutex so concurrent calls wait instead of being silently
dropped, ensuring the latest config is always applied.

Move blocking OS calls (networksetup on macOS) to spawn_blocking so
they no longer stall the tokio worker thread pool.

Frontend: release SwitchRow pendingRef in .finally() so the UI always
re-syncs with the actual OS proxy state, and rollback checked on error.

Closes #6614

* fix(changelog): add note for macOS proxy toggle freeze issue

src/components/shared/proxy-control-switches.tsx

@@ -67,10 +67,14 @@ const SwitchRow = ({
   const handleChange = (_: React.ChangeEvent, value: boolean) => {
     pendingRef.current = true
     setChecked(value)
-    onToggle(value).catch((err: any) => {
-      pendingRef.current = false
-      onError?.(err)
-    })
+    onToggle(value)
+      .catch((err: any) => {
+        setChecked(active)
+        onError?.(err)
+      })
+      .finally(() => {
+        pendingRef.current = false
+      })
   }
 
   return (