fix(macos): trigger Local Network permission prompt before server connect

The Local Network permission prompt (NWBrowser for _ts3._tcp) was
never actually triggered anywhere in the app. The service defined
triggerLocalNetworkPrompt() but no code called it.

Now _onConnect() checks the local network state before connecting.
If the state is unknown or notDetermined, it triggers the NWBrowser
scan which shows the system Local Network Privacy dialog on macOS 15+.
This ensures the prompt appears before the connection attempt so the
user can grant permission and the connection succeeds in one flow.

Non-macOS platforms are unaffected (short-circuited by the service).

apps/chanora_flutter/lib/main.dart

@@ -1067,6 +1067,18 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
     String? password,
   }) async {
     final connectEpoch = ++_connectionEpoch;
+
+    // Trigger macOS Local Network permission prompt before connecting.
+    // On macOS 15+ the first network connection triggers the system
+    // dialog; triggering it via NWBrowser here ensures the prompt
+    // appears *before* the actual connect attempt so the user can grant
+    // permission and the connection succeeds in one flow.
+    final lnState = _macOSPermissions.localNetworkState.value;
+    if (lnState == MacOSLocalNetworkState.unknown ||
+        lnState == MacOSLocalNetworkState.notDetermined) {
+      await _macOSPermissions.triggerLocalNetworkPrompt();
+    }
+
     setState(() {
       _phase = ConnectionPhase.connecting;
       _snapshot = null;