feat(bookshelf): add BookshelfViewModel, LibraryScreen and nav entry

- Create BookshelfViewModel (Hilt) for browsing remote libraries via BookshelfApiRepository.
- Create BookshelfLibraryScreen Compose UI: libraries list → items list.
- Add BOOKSHELF_LIBRARY_ROUTE to AppDestinations and wire composable in AppNavigation using hiltViewModel().
- Add Cloud icon button in LibraryScreen top bar to open server library.
- ':app:assembleOssDebug' passes.

app/src/main/java/com/dueattendant149/bookreader/reader/LibraryScreen.kt

@@ -80,6 +80,7 @@ import androidx.compose.material.icons.filled.Info
 import androidx.compose.material.icons.filled.MoreVert
 import androidx.compose.material.icons.filled.Search
 import androidx.compose.material.icons.filled.Settings
+import androidx.compose.material.icons.filled.Cloud
 import androidx.compose.material.icons.filled.Star
 import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.AssistChip
@@ -389,6 +390,7 @@ fun LibraryScreen(
             },
             onDeleteCatalogStreams = viewModel::deleteStreamedBooksForCatalog,
             onSettingsClick = { navController.navigate(AppDestinations.SETTINGS_SCREEN_ROUTE) },
+            onBookshelfClick = { navController.navigate(AppDestinations.BOOKSHELF_LIBRARY_ROUTE) },
             usePdfFileNameAsDisplayName = uiState.usePdfFileNameAsDisplayName
         )
 
@@ -663,6 +665,7 @@ fun LibraryScreenContent(
     onStreamOpdsBook: (OpdsEntry, OpdsCatalog?) -> Unit,
     onDeleteCatalogStreams: (String) -> Unit,
     onSettingsClick: () -> Unit,
+    onBookshelfClick: () -> Unit,
     usePdfFileNameAsDisplayName: Boolean,
 ) {
     val isBookContextualModeActive = selectedItems.isNotEmpty()
@@ -804,6 +807,9 @@ fun LibraryScreenContent(
                                     Icon(Icons.Default.Search, contentDescription = stringResource(R.string.action_search))
                                 }
                             }
+                            IconButton(onClick = onBookshelfClick) {
+                                Icon(Icons.Default.Cloud, contentDescription = "Server library")
+                            }
                             IconButton(onClick = onSettingsClick) {
                                 Icon(Icons.Default.Settings, contentDescription = stringResource(R.string.settings))
                             }