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.

AccessibilityTests/Sources/GeneratedAccessibilityTests.swift

@@ -411,6 +411,10 @@ extension AccessibilityTests {
         try await performAccessibilityAudit(named: "PlaceholderScreen_Previews")
     }
 
+    func testPlaybackSpeedButton() async throws {
+        try await performAccessibilityAudit(named: "PlaybackSpeedButton_Previews")
+    }
+
     func testPollFormScreen() async throws {
         try await performAccessibilityAudit(named: "PollFormScreen_Previews")
     }