refactor: Check server reachability on app resume instead of app start

- Move server check from init to onAppResume() in AppViewModel
- Add scenePhase observer in readeckApp
- Check only when app becomes active (.active phase)
- Respects 30s cache - won't call API if recently checked

readeck/UI/AppViewModel.swift

@@ -24,7 +24,6 @@ class AppViewModel: ObservableObject {
 
         Task {
             await loadSetupStatus()
-            await checkServerReachability()
         }
     }
     
@@ -70,6 +69,11 @@ class AppViewModel: ObservableObject {
         hasFinishedSetup = settingsRepository.hasFinishedSetup
     }
 
+    @MainActor
+    func onAppResume() async {
+        await checkServerReachability()
+    }
+
     @MainActor
     private func checkServerReachability() async {
         isServerReachable = await checkServerReachabilityUseCase.execute()

readeck/UI/readeckApp.swift

@@ -12,6 +12,7 @@ import netfox
 struct readeckApp: App {
     @StateObject private var appViewModel = AppViewModel()
     @StateObject private var appSettings = AppSettings()
+    @Environment(\.scenePhase) private var scenePhase
 
     var body: some Scene {
         WindowGroup {
@@ -38,6 +39,13 @@ struct readeckApp: App {
                     await loadAppSettings()
                 }
             }
+            .onChange(of: scenePhase) { oldPhase, newPhase in
+                if newPhase == .active {
+                    Task {
+                        await appViewModel.onAppResume()
+                    }
+                }
+            }
         }
     }