refactor(accessibility): simplify label handling

lib/features/sleep_timer/view/sleep_timer_button.dart

@@ -15,6 +15,8 @@ import 'package:vaani/shared/extensions/duration_format.dart';
 class SleepTimerButton extends HookConsumerWidget {
   const SleepTimerButton({super.key});
 
+  static const _sleepTimerLabel = 'Sleep timer';
+
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final sleepTimer = ref.watch(sleepTimerProvider);
@@ -23,10 +25,10 @@ class SleepTimerButton extends HookConsumerWidget {
     // if sleep timer is not active, show the button with the sleep timer icon
     // if the sleep timer is active, show the remaining time in a pill shaped container
     return Tooltip(
-      message: 'Sleep Timer',
+      message: _sleepTimerLabel,
       child: Semantics(
         button: true,
-        label: 'Sleep timer',
+        label: _sleepTimerLabel,
         child: InkWell(
           onTap: () async {
             appLogger.fine('Sleep Timer button pressed');

lib/shared/widgets/shelves/book_shelf.dart

@@ -206,6 +206,27 @@ class _BookOnShelfPlayButton extends HookConsumerWidget {
   /// the id of the library item of the book
   final String libraryItemId;
 
+  String getPlayTooltip({
+    required bool isCurrentBookSetInPlayer,
+    required bool isPlayingThisBook,
+    required bool isBookCompleted,
+    required bool hasProgress,
+  }) {
+    if (isCurrentBookSetInPlayer) {
+      return isPlayingThisBook ? 'Pause' : 'Resume';
+    }
+
+    if (isBookCompleted) {
+      return 'Listen again';
+    }
+
+    if (hasProgress) {
+      return 'Continue listening';
+    }
+
+    return 'Start listening';
+  }
+
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final me = ref.watch(meProvider);
@@ -218,15 +239,12 @@ class _BookOnShelfPlayButton extends HookConsumerWidget {
       (element) => element.libraryItemId == libraryItemId,
     );
     final isBookCompleted = userProgress?.isFinished ?? false;
-    final playTooltip = isCurrentBookSetInPlayer
-        ? isPlayingThisBook
-              ? 'Pause'
-              : 'Resume'
-        : isBookCompleted
-        ? 'Listen again'
-        : userProgress?.progress != null
-        ? 'Continue listening'
-        : 'Start listening';
+    final playTooltip = getPlayTooltip(
+      isCurrentBookSetInPlayer: isCurrentBookSetInPlayer,
+      isPlayingThisBook: isPlayingThisBook,
+      isBookCompleted: isBookCompleted,
+      hasProgress: userProgress?.progress != null,
+    );
 
     const size = 40.0;