feat(android): Library AppBar — Shuffle all button

Audit v2 #22. LibraryRepository.shuffleLibrary wraps the existing
LibraryApi.shuffleLibrary endpoint; LibraryViewModel.shuffleAll
fires PlayerController.setQueue with the response. LibraryScreen's
TopAppBar gains a Lucide.Shuffle IconButton to the left of the
existing MainAppBarActions row.

Offline-fallback (client-side shuffle over the local cache index)
is part of the larger Connectivity slice (audit #21) and not wired
in this commit — pressing Shuffle when offline just fails silently
for now.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/library/data/LibraryRepository.kt

@@ -121,4 +121,16 @@ class LibraryRepository @Inject constructor(
         val wire = api.getTrack(id)
         trackDao.upsertAll(listOf(wire.toEntity()))
     }
+
+    /**
+     * "Shuffle all" — server picks random tracks across the entire
+     * library. Backs the Library AppBar Shuffle button. No cache hit;
+     * the user-facing semantics are "give me something fresh".
+     */
+    suspend fun shuffleLibrary(limit: Int = SHUFFLE_DEFAULT_LIMIT): List<TrackRef> =
+        api.shuffleLibrary(limit = limit).map { it.toDomain() }
+
+    private companion object {
+        const val SHUFFLE_DEFAULT_LIMIT = 100
+    }
 }

android/app/src/main/java/com/fabledsword/minstrel/library/ui/LibraryScreen.kt

@@ -11,6 +11,8 @@ import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.foundation.lazy.grid.items
 import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.PrimaryScrollableTabRow
 import androidx.compose.material3.Scaffold
@@ -83,6 +85,13 @@ fun LibraryScreen(
                 TopAppBar(
                     title = { Text("Library") },
                     actions = {
+                        IconButton(onClick = viewModel::shuffleAll) {
+                            Icon(
+                                imageVector = com.composables.icons.lucide.Lucide.Shuffle,
+                                contentDescription = "Shuffle all",
+                                tint = MaterialTheme.colorScheme.onSurface,
+                            )
+                        }
                         MainAppBarActions(
                             navController = navController,
                             currentRouteName = Library::class.qualifiedName,

android/app/src/main/java/com/fabledsword/minstrel/library/ui/LibraryViewModel.kt

@@ -18,8 +18,9 @@ private const val SHARE_STOP_TIMEOUT_MS = 5_000L
 
 @HiltViewModel
 class LibraryViewModel @Inject constructor(
-    repository: LibraryRepository,
+    private val repository: LibraryRepository,
     private val syncController: SyncController,
+    private val player: com.fabledsword.minstrel.player.PlayerController,
 ) : ViewModel() {
 
     val uiState: StateFlow<LibraryUiState> =
@@ -50,4 +51,21 @@ class LibraryViewModel @Inject constructor(
     fun refresh(): Job = viewModelScope.launch {
         syncController.syncSafe()
     }
+
+    /**
+     * "Shuffle all" — fetches a random sample across the entire
+     * library and starts playback. Silent on transport failure (user
+     * can re-tap; the action has no inline error surface).
+     */
+    fun shuffleAll() {
+        viewModelScope.launch {
+            runCatching {
+                val tracks = repository.shuffleLibrary()
+                    .filter { it.streamUrl.isNotEmpty() }
+                if (tracks.isNotEmpty()) {
+                    player.setQueue(tracks, initialIndex = 0, source = "library_shuffle")
+                }
+            }
+        }
+    }
 }