feat: implement quick play/pause toggle for TV player

Adds the ability to play and pause media using the Center or Enter keys
without displaying the full player controls. When pausing via this
method, a brief visual "Pause" feedback overlay is shown in the center
of the screen.

- Added `TvPlayerHiddenStopFeedback` component and related logic
- Updated `handleTvPlayerRootKeyEvent` to support background playback toggling
- Added `pausePlayback` and `resumePlayback` to `PlayerViewModel` and `PlayerManager`
- Included comprehensive UI tests for the new hidden control behavior

core/player/src/main/java/hu/bbara/purefin/core/player/manager/PlayerManager.kt

@@ -139,6 +139,18 @@ class PlayerManager @Inject constructor(
         if (player.isPlaying) player.pause() else player.play()
     }
 
+    fun pausePlayback() {
+        if (player.isPlaying) {
+            player.pause()
+        }
+    }
+
+    fun resumePlayback() {
+        if (!player.isPlaying) {
+            player.play()
+        }
+    }
+
     fun seekTo(positionMs: Long) {
         val target = clampSeekPosition(positionMs)
         pendingSeekPositionMs = target

core/player/src/main/java/hu/bbara/purefin/core/player/viewmodel/PlayerViewModel.kt

@@ -188,6 +188,14 @@ class PlayerViewModel @Inject constructor(
         showControls(autoHideDelayMs)
     }
 
+    fun pausePlayback() {
+        playerManager.pausePlayback()
+    }
+
+    fun resumePlayback() {
+        playerManager.resumePlayback()
+    }
+
     fun seekTo(positionMs: Long) {
         playerManager.seekTo(positionMs)
     }