feat: add smart download feature for series

Automatically manages downloaded episodes per series — keeps 5 unwatched
episodes downloaded, removing watched ones and fetching new ones on
HomeScreen open or pull-to-refresh. A single download button on the
Series screen opens a dialog to choose between downloading all episodes
or enabling smart download.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

feature/shared/src/main/java/hu/bbara/purefin/feature/shared/content/series/SeriesViewModel.kt

@@ -39,6 +39,13 @@ class SeriesViewModel @Inject constructor(
         }
         .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), null)
 
+    @OptIn(ExperimentalCoroutinesApi::class)
+    val isSmartDownloadEnabled: StateFlow<Boolean> = _seriesId
+        .flatMapLatest { id ->
+            if (id != null) mediaDownloadManager.isSmartDownloadEnabled(id) else flowOf(false)
+        }
+        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), false)
+
     private val _seriesDownloadState = MutableStateFlow<DownloadState>(DownloadState.NotDownloaded)
     val seriesDownloadState: StateFlow<DownloadState> = _seriesDownloadState
 
@@ -76,6 +83,16 @@ class SeriesViewModel @Inject constructor(
         }
     }
 
+    fun toggleSmartDownload(seriesId: UUID) {
+        viewModelScope.launch {
+            if (isSmartDownloadEnabled.value) {
+                mediaDownloadManager.disableSmartDownload(seriesId)
+            } else {
+                mediaDownloadManager.enableSmartDownload(seriesId)
+            }
+        }
+    }
+
     fun downloadSeries(series: Series) {
         viewModelScope.launch {
             val allEpisodeIds = series.seasons.flatMap { season ->

feature/shared/src/main/java/hu/bbara/purefin/feature/shared/home/HomePageViewModel.kt

@@ -12,6 +12,7 @@ import hu.bbara.purefin.core.data.navigation.NavigationManager
 import hu.bbara.purefin.core.data.navigation.Route
 import hu.bbara.purefin.core.data.navigation.SeriesDto
 import hu.bbara.purefin.core.data.session.UserSessionRepository
+import hu.bbara.purefin.feature.download.MediaDownloadManager
 import hu.bbara.purefin.core.model.Media
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -31,7 +32,8 @@ class HomePageViewModel @Inject constructor(
     private val appContentRepository: AppContentRepository,
     private val userSessionRepository: UserSessionRepository,
     private val navigationManager: NavigationManager,
-    private val refreshHomeDataUseCase: RefreshHomeDataUseCase
+    private val refreshHomeDataUseCase: RefreshHomeDataUseCase,
+    private val mediaDownloadManager: MediaDownloadManager,
 ) : ViewModel() {
 
     private val _isRefreshing = MutableStateFlow(false)
@@ -199,6 +201,11 @@ class HomePageViewModel @Inject constructor(
                 // Refresh is best-effort; don't crash on failure
             }
         }
+        viewModelScope.launch {
+            try {
+                mediaDownloadManager.syncSmartDownloads()
+            } catch (_: Exception) { }
+        }
     }
 
     fun onRefresh() {
@@ -212,6 +219,11 @@ class HomePageViewModel @Inject constructor(
                 _isRefreshing.value = false
             }
         }
+        viewModelScope.launch {
+            try {
+                mediaDownloadManager.syncSmartDownloads()
+            } catch (_: Exception) { }
+        }
     }
 
     fun logout() {