fix(android): render widgets in fullscreen / single-zone layouts

Widgets worked in multi-zone layouts (ZoneManager renders them in a WebView) but
were broken in "default fullscreen" (no layout) and the fullscreen template (a
single-zone layout) - both take the single-zone PlaylistController path, which:
  1) called getString("content_id"), throwing on a widget assignment (no
     content_id) - in both the playlist builder AND the pre-download loop, which
     could break the whole fullscreen playlist; and
  2) had no widget render case in playItem (so a widget never displayed).

Fix:
- PlaylistItem gains widgetId/widgetType + isWidget; the builder reads them and
  tolerates a missing content_id.
- playItem renders a widget fullscreen via MediaPlayerManager.showWidget() (loads
  /api/widgets/:id/render in the full-screen WebView, mirroring ZoneManager).
- Widgets auto-advance on their duration like images.
- Pre-download loop skips widget assignments (no file to fetch).

Compile-checked; signed APK builds. Needs on-device check: a widget plays in
default-fullscreen and the fullscreen template, and mixed widget+media playlists
advance correctly.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/remotedisplay/player/MainActivity.kt

@@ -260,7 +260,12 @@ class MainActivity : AppCompatActivity() {
             thread {
                 for (i in 0 until assignments.length()) {
                     val item = assignments.getJSONObject(i)
-                    val contentId = item.getString("content_id")
+                    // Widget assignments have no downloadable content file - skip
+                    // (also avoids getString throwing on a null content_id).
+                    val widgetId = if (item.isNull("widget_id")) "" else item.optString("widget_id", "")
+                    if (widgetId.isNotEmpty()) continue
+                    val contentId = if (item.isNull("content_id")) "" else item.optString("content_id", "")
+                    if (contentId.isEmpty()) continue
                     val filename = item.optString("filename", "content")
                     val remoteUrl = item.optString("remote_url", null)
 
@@ -416,6 +421,17 @@ class MainActivity : AppCompatActivity() {
     private fun playItem(item: PlaylistItem) {
         hideStatus()
 
+        // Widget content - render fullscreen in a WebView (single-zone / fullscreen
+        // layouts; multi-zone widgets go through ZoneManager). Previously unhandled,
+        // so widgets were blank/broken in default-fullscreen and the fullscreen template.
+        if (item.isWidget) {
+            val url = "${config.serverUrl}/api/widgets/${item.widgetId}/render"
+            Log.i("MainActivity", "Playing widget fullscreen: $url")
+            mediaPlayer.showWidget(url)
+            wsService?.sendPlaybackState(item.contentId.ifEmpty { item.widgetId ?: "" }, 0f)
+            return
+        }
+
         // YouTube content - play in WebView
         if (item.mimeType == "video/youtube" && !item.remoteUrl.isNullOrEmpty()) {
             Log.i("MainActivity", "Playing YouTube: ${item.remoteUrl}")

android/app/src/main/java/com/remotedisplay/player/player/MediaPlayerManager.kt

@@ -25,7 +25,7 @@ class MediaPlayerManager(
     private var exoPlayer: ExoPlayer? = null
     private var currentType: MediaType = MediaType.NONE
 
-    enum class MediaType { NONE, VIDEO, IMAGE, YOUTUBE }
+    enum class MediaType { NONE, VIDEO, IMAGE, YOUTUBE, WIDGET }
 
     init {
         setupExoPlayer()
@@ -65,6 +65,29 @@ class MediaPlayerManager(
         }
     }
 
+    // Fullscreen widget render (single-zone / "fullscreen" layouts). Reuses the
+    // full-screen WebView; ZoneManager handles widgets in multi-zone layouts.
+    fun showWidget(url: String) {
+        Log.i("MediaPlayerManager", "Showing widget: $url")
+        currentType = MediaType.WIDGET
+
+        playerView.visibility = android.view.View.GONE
+        imageView.visibility = android.view.View.GONE
+        youtubeWebView?.visibility = android.view.View.VISIBLE
+
+        exoPlayer?.stop()
+
+        youtubeWebView?.apply {
+            settings.javaScriptEnabled = true
+            settings.domStorageEnabled = true
+            settings.mediaPlaybackRequiresUserGesture = false
+            webViewClient = WebViewClient()
+            webChromeClient = WebChromeClient()
+            setBackgroundColor(android.graphics.Color.TRANSPARENT)
+            loadUrl(url)
+        }
+    }
+
     fun playVideoFromUrl(url: String, muted: Boolean = false) {
         Log.i("MediaPlayerManager", "Streaming video from URL: $url (muted=$muted)")
         currentType = MediaType.VIDEO

android/app/src/main/java/com/remotedisplay/player/player/PlaylistController.kt

@@ -17,9 +17,13 @@ data class PlaylistItem(
     val sortOrder: Int,
     val enabled: Boolean = true,
     val remoteUrl: String? = null,
-    val muted: Boolean = false
+    val muted: Boolean = false,
+    val widgetId: String? = null,
+    val widgetType: String? = null
 ) {
     val isRemote: Boolean get() = !remoteUrl.isNullOrEmpty()
+    // Widget assignments have a widget_id and no downloadable content file.
+    val isWidget: Boolean get() = !widgetId.isNullOrEmpty()
 }
 
 class PlaylistController(
@@ -51,7 +55,8 @@ class PlaylistController(
             newItems.add(
                 PlaylistItem(
                     assignmentId = obj.optInt("id", 0),
-                    contentId = obj.getString("content_id"),
+                    // Tolerant: widget assignments have no content_id (getString threw).
+                    contentId = if (obj.isNull("content_id")) "" else obj.optString("content_id", ""),
                     filename = obj.optString("filename", "unknown"),
                     mimeType = obj.optString("mime_type", "video/mp4"),
                     filepath = obj.optString("filepath", ""),
@@ -60,14 +65,17 @@ class PlaylistController(
                     sortOrder = obj.optInt("sort_order", 0),
                     enabled = obj.optInt("enabled", 1) == 1,
                     remoteUrl = if (obj.isNull("remote_url")) null else obj.optString("remote_url", "").ifEmpty { null },
-                    muted = obj.optInt("muted", 0) == 1
+                    muted = obj.optInt("muted", 0) == 1,
+                    widgetId = if (obj.isNull("widget_id")) null else obj.optString("widget_id", "").ifEmpty { null },
+                    widgetType = if (obj.isNull("widget_type")) null else obj.optString("widget_type", "").ifEmpty { null }
                 )
             )
         }
 
-        // Check if playlist actually changed
-        val oldContentIds = items.map { it.contentId }
-        val newContentIds = newItems.map { it.contentId }
+        // Check if playlist actually changed (key on content OR widget id, since
+        // widget items share an empty contentId).
+        val oldContentIds = items.map { it.contentId + "|" + (it.widgetId ?: "") }
+        val newContentIds = newItems.map { it.contentId + "|" + (it.widgetId ?: "") }
         val playlistChanged = oldContentIds != newContentIds
 
         if (!playlistChanged && items.isNotEmpty()) {
@@ -169,8 +177,9 @@ class PlaylistController(
         Log.i("PlaylistController", "Playing: ${item.filename} (index $currentIndex)")
         onItemChanged(item)
 
-        // For images, auto-advance after duration. For videos, wait for completion callback.
-        if (item.mimeType.startsWith("image/")) {
+        // For images and widgets, auto-advance after duration. For videos, wait
+        // for the completion callback.
+        if (item.mimeType.startsWith("image/") || item.isWidget) {
             scheduleAdvance(item.durationSec * 1000L)
         }
     }