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(

app/src/main/java/org/dueattendant149/bookreader/ServerSettingsScreen.kt

@@ -0,0 +1,114 @@
+package org.dueattendant149.bookreader.bookshelf
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material3.Button
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.input.PasswordVisualTransformation
+import androidx.compose.ui.text.input.VisualTransformation
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun ServerSettingsScreen(
+    viewModel: ServerSettingsViewModel,
+    onBackClick: () -> Unit,
+) {
+    val uiState by viewModel.uiState.collectAsStateWithLifecycle()
+    var bookshelfUrl by remember(uiState.bookshelfUrl) { androidx.compose.runtime.mutableStateOf(uiState.bookshelfUrl) }
+    var absUrl by remember(uiState.absUrl) { androidx.compose.runtime.mutableStateOf(uiState.absUrl) }
+    var absToken by remember(uiState.absToken) { androidx.compose.runtime.mutableStateOf(uiState.absToken) }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("Server settings") },
+                navigationIcon = {
+                    IconButton(onClick = onBackClick) {
+                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back")
+                    }
+                }
+            )
+        }
+    ) { padding ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(padding)
+                .padding(16.dp)
+        ) {
+            Text("Bookshelf API")
+            Spacer(modifier = Modifier.height(8.dp))
+            OutlinedTextField(
+                value = bookshelfUrl,
+                onValueChange = {
+                    bookshelfUrl = it
+                    viewModel.updateBookshelfUrl(it)
+                },
+                label = { Text("https://books.dueattendant149.org/") },
+                singleLine = true,
+                modifier = Modifier.fillMaxWidth()
+            )
+
+            Spacer(modifier = Modifier.height(24.dp))
+
+            Text("Audiobookshelf")
+            Spacer(modifier = Modifier.height(8.dp))
+            OutlinedTextField(
+                value = absUrl,
+                onValueChange = {
+                    absUrl = it
+                    viewModel.updateAbsUrl(it)
+                },
+                label = { Text("https://abs.dueattendant149.org/") },
+                singleLine = true,
+                modifier = Modifier.fillMaxWidth()
+            )
+            Spacer(modifier = Modifier.height(8.dp))
+            OutlinedTextField(
+                value = absToken,
+                onValueChange = {
+                    absToken = it
+                    viewModel.updateAbsToken(it)
+                },
+                label = { Text("Bearer token") },
+                singleLine = true,
+                visualTransformation = PasswordVisualTransformation(),
+                modifier = Modifier.fillMaxWidth()
+            )
+
+            Spacer(modifier = Modifier.height(24.dp))
+
+            Button(
+                onClick = viewModel::save,
+                modifier = Modifier.fillMaxWidth()
+            ) {
+                Text("Save")
+            }
+
+            if (uiState.saved) {
+                Spacer(modifier = Modifier.height(8.dp))
+                Text("Saved")
+            }
+        }
+    }
+}

app/src/main/java/org/dueattendant149/bookreader/ServerSettingsViewModel.kt

@@ -0,0 +1,58 @@
+package org.dueattendant149.bookreader.bookshelf
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
+import org.dueattendant149.bookreader.data.settings.ServerSettings
+import javax.inject.Inject
+
+data class ServerSettingsUiState(
+    val bookshelfUrl: String = "",
+    val absUrl: String = "",
+    val absToken: String = "",
+    val saved: Boolean = false,
+)
+
+@HiltViewModel
+class ServerSettingsViewModel
+    @Inject
+    constructor(
+        private val serverSettings: ServerSettings,
+    ) : ViewModel() {
+
+        private val _uiState = MutableStateFlow(ServerSettingsUiState())
+        val uiState: StateFlow<ServerSettingsUiState> = _uiState.asStateFlow()
+
+        init {
+            _uiState.value = ServerSettingsUiState(
+                bookshelfUrl = serverSettings.getBookshelfUrl() ?: "",
+                absUrl = serverSettings.getAbsUrl() ?: "",
+                absToken = serverSettings.getAbsToken() ?: "",
+            )
+        }
+
+        fun updateBookshelfUrl(url: String) {
+            _uiState.value = _uiState.value.copy(bookshelfUrl = url, saved = false)
+        }
+
+        fun updateAbsUrl(url: String) {
+            _uiState.value = _uiState.value.copy(absUrl = url, saved = false)
+        }
+
+        fun updateAbsToken(token: String) {
+            _uiState.value = _uiState.value.copy(absToken = token, saved = false)
+        }
+
+        fun save() {
+            viewModelScope.launch {
+                serverSettings.setBookshelfUrl(_uiState.value.bookshelfUrl.trim())
+                serverSettings.setAbsUrl(_uiState.value.absUrl.trim())
+                serverSettings.setAbsToken(_uiState.value.absToken.trim())
+                _uiState.value = _uiState.value.copy(saved = true)
+            }
+        }
+    }

app/src/main/java/org/dueattendant149/bookreader/bookshelf/BookshelfLibraryScreen.kt

@@ -8,9 +8,13 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Settings
 import androidx.compose.material3.Card
 import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
 import androidx.compose.material3.LinearProgressIndicator
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
@@ -33,6 +37,7 @@ import org.dueattendant149.bookreader.data.remote.bookshelfapi.model.UnifiedItem
 fun BookshelfLibraryScreen(
     viewModel: BookshelfViewModel,
     onItemClick: (UnifiedItemResponse) -> Unit,
+    onOpenSettings: () -> Unit = {},
 ) {
     val uiState by viewModel.uiState.collectAsStateWithLifecycle()
 
@@ -46,6 +51,11 @@ fun BookshelfLibraryScreen(
         topBar = {
             TopAppBar(
                 title = { Text("Server Library") },
+                actions = {
+                    IconButton(onClick = onOpenSettings) {
+                        Icon(Icons.Default.Settings, contentDescription = "Server settings")
+                    }
+                }
             )
         }
     ) { padding ->