feat: show content title in download notification

Store the movie/episode title as UTF-8 bytes in DownloadRequest.data
when building each download request. PurefinDownloadService reads it
back in getForegroundNotification() so the notification shows the
actual title (e.g. "Inception") instead of the generic "Downloading".

For multiple simultaneous downloads the existing "Downloading N files"
text is kept. The title is persisted by Media3 alongside the request,
so it survives app restarts.

feature/download/src/main/java/hu/bbara/purefin/feature/download/MediaDownloadManager.kt

@@ -164,7 +164,9 @@ class MediaDownloadManager @Inject constructor(
                 offlineDataSource.saveMovies(listOf(movie))
 
                 Log.d(TAG, "Starting download for '${movie.title}' from: $url")
-                val request = DownloadRequest.Builder(movieId.toString(), url.toUri()).build()
+                val request = DownloadRequest.Builder(movieId.toString(), url.toUri())
+                    .setData(movie.title.toByteArray(Charsets.UTF_8))
+                    .build()
                 PurefinDownloadService.sendAddDownload(context, request)
                 Log.d(TAG, "Download request sent for $movieId")
             } catch (e: Exception) {
@@ -226,7 +228,9 @@ class MediaDownloadManager @Inject constructor(
                 offlineDataSource.saveEpisode(episode)
 
                 Log.d(TAG, "Starting download for episode '${episode.title}' from: $url")
-                val request = DownloadRequest.Builder(episodeId.toString(), url.toUri()).build()
+                val request = DownloadRequest.Builder(episodeId.toString(), url.toUri())
+                    .setData(episode.title.toByteArray(Charsets.UTF_8))
+                    .build()
                 PurefinDownloadService.sendAddDownload(context, request)
                 Log.d(TAG, "Download request sent for episode $episodeId")
             } catch (e: Exception) {

feature/download/src/main/java/hu/bbara/purefin/feature/download/PurefinDownloadService.kt

@@ -79,7 +79,10 @@ class PurefinDownloadService : DownloadService(
         }
 
         val title = if (activeDownloads.size == 1) {
-            "Downloading"
+            activeDownloads[0].request.data
+                ?.toString(Charsets.UTF_8)
+                ?.takeIf { it.isNotBlank() }
+                ?: "Downloading"
         } else {
             "Downloading ${activeDownloads.size} files"
         }