fix(proxy): sync system proxy switch state with background highlight #5240, #5439, #5421, #4651, #4536

Fixed race condition where button state and background color would desync
during rapid toggles or slow backend responses.

Root causes:
- Button used actualState while background used configState
- toggleSystemProxy returned immediately via setTimeout(0), releasing lock
  before backend operation completed
- 100ms delay in updateProxyStatus caused visual flash

Changes:
- Unified state source: both button and background now use actualState
- Made toggleSystemProxy truly async with proper await chain
- Wrapped toggle function with useLockFn to serialize operations
- Reduced state refresh delay from 100ms to 50ms
- Fixed GuardState lock release timing for async operations
- Added proper error rollback with state refresh on failure

Resolves issue where proxy toggle button would show as off while
background remained green, or vice versa.

src/components/shared/ProxyControlSwitches.tsx

@@ -123,7 +123,7 @@ const ProxyControlSwitches = ({
   const sysproxyRef = useRef<DialogRef>(null);
   const tunRef = useRef<DialogRef>(null);
 
-  const { enable_tun_mode, enable_system_proxy } = verge ?? {};
+  const { enable_tun_mode } = verge ?? {};
 
   const showErrorNotice = useCallback(
     (msg: string) => showNotice.error(msg),
@@ -175,7 +175,7 @@ const ProxyControlSwitches = ({
           onInfoClick={() => sysproxyRef.current?.open()}
           onToggle={(value) => toggleSystemProxy(value)}
           onError={onError}
-          highlight={enable_system_proxy}
+          highlight={systemProxyActualState}
         />
       )}