fix Swift 6 concurrency data races across AppState, UDPManager, SessionView

cue-ios/CueIOS/AppState.swift

@@ -576,8 +576,9 @@ final class AppState {
         transport.measuring = true
         send(buildSysexStartClean(vMv: v, durationS: d))
         status = String(format: "Cleaning: %.0f mV for %.0fs", v, d)
-        DispatchQueue.main.asyncAfter(deadline: .now() + Double(d) + 2) { [weak self] in
-            self?.transport.measuring = false
+        let t = transport
+        DispatchQueue.main.asyncAfter(deadline: .now() + Double(d) + 2) {
+            t.measuring = false
         }
     }
 

cue-ios/CueIOS/Transport/UDPManager.swift

@@ -72,8 +72,9 @@ final class UDPManager: @unchecked Sendable {
         connection = conn
 
         conn.stateUpdateHandler = { [weak self] newState in
+            guard let self else { return }
             DispatchQueue.main.async {
-                self?.handleStateChange(newState)
+                self.handleStateChange(newState)
             }
         }
 
@@ -184,7 +185,8 @@ final class UDPManager: @unchecked Sendable {
 
     private func startTimers() {
         keepaliveTimer = Timer.scheduledTimer(withTimeInterval: Self.keepaliveInterval, repeats: true) { [weak self] _ in
-            self?.send(buildSysexGetTemp())
+            guard let self else { return }
+            self.send(buildSysexGetTemp())
         }
 
         timeoutTimer = Timer.scheduledTimer(withTimeInterval: 2, repeats: true) { [weak self] _ in

cue-ios/CueIOS/Views/SessionView.swift

@@ -28,7 +28,9 @@ struct SessionView: View {
 
     private func startObserving() {
         sessionCancellable = Storage.shared.observeSessions { sessions in
-            self.sessions = sessions
+            Task { @MainActor in
+                self.sessions = sessions
+            }
         }
     }