feat: add fallback tunnel status check and improve Windows service command calls

Add fallback to tunnel_status when metrics query fails in current_metrics function, returning zero bytes with actual tunnel state. Update waitForTunnelStatus in frontend to use tunnel_status instead of tunnel_metrics for status polling and refresh metrics separately on success. Change CloseRequested window event handler to call app_handle().exit(0) instead of no-op. Replace "sc" with "sc.exe" in all Windows service command

desktop-client/src/App.tsx

@@ -88,7 +88,14 @@ export function App() {
       setMetrics(value);
       setConnected(value.active);
     } catch {
-      setMetrics({ active: false, rxBytes: 0, txBytes: 0 });
+      try {
+        const active = await invoke<boolean>("tunnel_status");
+        setConnected(active);
+        setMetrics((current) => ({ ...current, active }));
+      } catch {
+        setMetrics({ active: false, rxBytes: 0, txBytes: 0 });
+        setConnected(false);
+      }
     }
   }
 
@@ -122,15 +129,16 @@ export function App() {
   async function waitForTunnelStatus(expected: boolean) {
     for (let attempt = 0; attempt < 8; attempt += 1) {
       try {
-        const value = await invoke<TunnelMetrics>("tunnel_metrics");
-        setMetrics(value);
-        setConnected(value.active);
-        if (value.active === expected) {
-          return value.active;
+        const active = await invoke<boolean>("tunnel_status");
+        setConnected(active);
+        if (active === expected) {
+          await refreshTunnelMetrics();
+          return active;
         }
       } catch {
         if (!expected) {
           setMetrics({ active: false, rxBytes: 0, txBytes: 0 });
+          setConnected(false);
           return false;
         }
       }
@@ -138,11 +146,11 @@ export function App() {
       await new Promise((resolve) => window.setTimeout(resolve, 500));
     }
 
-    return invoke<TunnelMetrics>("tunnel_metrics")
-      .then((value) => {
-        setMetrics(value);
-        setConnected(value.active);
-        return value.active;
+    return invoke<boolean>("tunnel_status")
+      .then(async (active) => {
+        setConnected(active);
+        await refreshTunnelMetrics();
+        return active;
       })
       .catch(() => false);
   }