feat(bookshelf): add ServerSettingsScreen for bookshelf-api/ABS config

- Create ServerSettingsViewModel (Hilt) backed by SharedPreferences ServerSettings.
- Create ServerSettingsScreen Compose UI with URL/token fields and Save button.
- Add SERVER_SETTINGS_ROUTE to AppDestinations and wire in AppNavigation.
- Add settings icon in BookshelfLibraryScreen top bar to open settings.
- ':app:assembleOssDebug' passes.

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

@@ -83,6 +83,7 @@ object AppDestinations {
     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"
+    const val SERVER_SETTINGS_ROUTE = "server_settings"
 }
 
 fun shouldInterceptAppNavBack(
@@ -438,9 +439,20 @@ fun AppNavigation(
                 viewModel = bookshelfViewModel,
                 onItemClick = { item ->
                     Timber.d("Bookshelf item selected: ${item.id}")
+                },
+                onOpenSettings = {
+                    navController.navigateIfReady(AppDestinations.SERVER_SETTINGS_ROUTE)
                 }
             )
         }
+
+        composable(route = AppDestinations.SERVER_SETTINGS_ROUTE) {
+            val settingsViewModel: org.dueattendant149.bookreader.bookshelf.ServerSettingsViewModel = hiltViewModel()
+            org.dueattendant149.bookreader.bookshelf.ServerSettingsScreen(
+                viewModel = settingsViewModel,
+                onBackClick = { navController.popBackStackIfReady() }
+            )
+        }
         }
 
         AnimatedVisibility(