Keep the iPhone screen awake for the whole app session

Move the idle-timer disable out of ExerciseView/ExerciseProgressView and
up to the app scene, re-asserting it whenever the scene becomes active
(iOS clears the flag on background). A propped-up phone now stays lit for
the entire workout, not just while an exercise is open.

Claude-Session: https://claude.ai/code/session_01SCv7zvGFcKy47KSTnTLxRe

Workouts/WorkoutsApp.swift

@@ -7,10 +7,12 @@
 
 import SwiftUI
 import SwiftData
+import UIKit
 
 @main
 struct WorkoutsApp: App {
     @State private var services = AppServices()
+    @Environment(\.scenePhase) private var scenePhase
 
     var body: some Scene {
         WindowGroup {
@@ -24,6 +26,12 @@ struct WorkoutsApp: App {
             root
             #endif
         }
+        // Keep the screen lit for the whole app, not just while logging — the phone is
+        // often propped up across the room during a workout. iOS clears this flag when
+        // the app is backgrounded, so re-assert it each time the scene becomes active.
+        .onChange(of: scenePhase, initial: true) { _, phase in
+            UIApplication.shared.isIdleTimerDisabled = (phase == .active)
+        }
     }
 
     private var root: some View {