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/AppNavigation.kt

@@ -52,6 +52,8 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.platform.LocalContext
+import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.media3.common.util.UnstableApi
@@ -59,6 +61,7 @@ import androidx.navigation.NavHostController
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.currentBackStackEntryAsState
+import org.dueattendant149.bookreader.bookshelf.BookshelfLibraryScreen
 import org.dueattendant149.bookreader.epubreader.EpubReaderScreen
 import org.dueattendant149.bookreader.feedback.FeedbackScreen
 import org.dueattendant149.bookreader.feedback.SupportProjectScreen
@@ -79,6 +82,7 @@ object AppDestinations {
     const val FONTS_SCREEN_ROUTE = "fonts_screen_route"
     const val AI_SETTINGS_SCREEN_ROUTE = "ai_settings_screen_route"
     const val SETTINGS_SCREEN_ROUTE = "settings_screen_route"
+    const val BOOKSHELF_LIBRARY_ROUTE = "bookshelf_library"
 }
 
 fun shouldInterceptAppNavBack(
@@ -427,6 +431,16 @@ fun AppNavigation(
                 onBackClick = { navController.popBackStackIfReady() }
             )
         }
+
+        composable(route = AppDestinations.BOOKSHELF_LIBRARY_ROUTE) {
+            val bookshelfViewModel: org.dueattendant149.bookreader.bookshelf.BookshelfViewModel = hiltViewModel()
+            BookshelfLibraryScreen(
+                viewModel = bookshelfViewModel,
+                onItemClick = { item ->
+                    Timber.d("Bookshelf item selected: ${item.id}")
+                }
+            )
+        }
         }
 
         AnimatedVisibility(