Voice message: variable play back speed (#5121)

* Implement voice message variable playback speed

* Move playback speed string to Untranslated

https://github.com/element-hq/element-x-ios/pull/5121#discussion_r2822631371

* Address review feedback for voice message playback speed

- Persist voice message playback speed as an enum in AppSettings instead of storing an index.
- Update playback speed cycling to derive from enum allCases and safely fall back to `.default` if the stored value cannot be resolved.
- Apply runtime speed updates in AudioPlayer only when the player is in the `.playing` state.
- Keep MediaPlayerProviderTests formatting/indentation style intact while retaining mock playback speed setup.
- Regenerate preview snapshots for:
  - PlaybackSpeedButton
  - VoiceMessageRoomPlaybackView
  - VoiceMessageRoomTimelineView

* Move VoiceMessagePlaybackSpeed outside AppSettings, remove speedRatio

* Stabilize PlaybackSpeedButton width

* Sync voice-message speed label

- Add voiceMessagePlaybackSpeed to TimelineViewState and bind it from appSettings.$voiceMessagePlaybackSpeed.
- Pass that timeline-level speed into VoiceMessageRoomPlaybackView and use it for PlaybackSpeedButton, so labels update consistently across items.
- Use @EnvironmentObject in VoiceMessageRoomTimelineContent so the view re-renders when timeline context state changes.
- In WaveformInteractionModifier, add .allowsHitTesting(showCursor) to the cursor interaction view so hidden pre-playback cursor hit area does not steal taps from the speed button.

ElementX/Sources/Other/TestablePreview/TestablePreviewsDictionary.swift

@@ -110,6 +110,7 @@ enum TestablePreviewsDictionary {
         "PinnedItemsIndicatorView_Previews" : PinnedItemsIndicatorView_Previews.self,
         "PlaceholderAvatarImage_Previews" : PlaceholderAvatarImage_Previews.self,
         "PlaceholderScreen_Previews" : PlaceholderScreen_Previews.self,
+        "PlaybackSpeedButton_Previews" : PlaybackSpeedButton_Previews.self,
         "PollFormScreen_Previews" : PollFormScreen_Previews.self,
         "PollOptionView_Previews" : PollOptionView_Previews.self,
         "PollRoomTimelineView_Previews" : PollRoomTimelineView_Previews.self,