feat: add dark mode with toggle in top bar

- Created UnoTheme.kt with light/dark color schemes
- Added dark mode toggle (moon/sun icon) in GameInfoBar
- Wrapped all entry points (Desktop, Android, Web) with UnoTheme
- Fixed Web entry point to use CanvasBasedWindow
- Fixed Math.random() for WASM compatibility

androidApp/src/androidMain/kotlin/com/uno/android/MainActivity.kt

@@ -13,6 +13,7 @@ import androidx.compose.ui.unit.dp
 import com.uno.game.GameEngine
 import com.uno.game.model.*
 import com.uno.shared.UnoGameScreen
+import com.uno.shared.UnoTheme
 import kotlinx.coroutines.delay
 
 class MainActivity : ComponentActivity() {
@@ -20,7 +21,7 @@ class MainActivity : ComponentActivity() {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         setContent {
-            MaterialTheme {
+            UnoTheme {
                 Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {
                     UnoApp()
                 }

desktopApp/src/jvmMain/kotlin/com/uno/desktop/Main.kt

@@ -13,6 +13,7 @@ import androidx.compose.ui.window.application
 import com.uno.game.GameEngine
 import com.uno.game.model.*
 import com.uno.shared.UnoGameScreen
+import com.uno.shared.UnoTheme
 import kotlinx.coroutines.delay
 
 fun main() = application {
@@ -49,6 +50,7 @@ fun UnoDesktopApp() {
         }
     }
 
+    UnoTheme {
         if (!gameStarted) {
             DesktopStartScreen(onStartGame = { playerCount ->
                 gameState = engine.startGame(playerCount)
@@ -76,6 +78,7 @@ fun UnoDesktopApp() {
                 )
             }
         }
+    }
 }
 
 @Composable

shared/src/commonMain/kotlin/com/uno/shared/UnoGameScreen.kt

@@ -63,7 +63,7 @@ private class FlyingCardState {
         animatableX = Animatable(fromX)
         animatableY = Animatable(fromY)
         animatableScale = Animatable(0.3f)
-        animatableRotation = Animatable((Math.random() * 60 - 30).toFloat())
+        animatableRotation = Animatable((kotlin.random.Random.nextFloat() * 60 - 30).toFloat())
 
         coroutineScope {
             launch {
@@ -274,6 +274,7 @@ fun UnoGameScreen(
     var previousLastAction by remember { mutableStateOf(state.lastAction) }
     var previousTopCard by remember { mutableStateOf(state.deck.topCard) }
     var lastPlayedByPlayerIndex by remember { mutableIntStateOf(0) }
+    var isDarkMode by remember { mutableStateOf(false) }
 
     val flyingState = rememberFlyingCardState()
 
@@ -317,6 +318,7 @@ fun UnoGameScreen(
         previousLastAction = state.lastAction
     }
 
+    UnoTheme(darkTheme = isDarkMode) {
         Box(modifier = Modifier.fillMaxSize()) {
             Column(
                 modifier = Modifier
@@ -324,7 +326,7 @@ fun UnoGameScreen(
                     .padding(16.dp),
                 horizontalAlignment = Alignment.CenterHorizontally
             ) {
-            GameInfoBar(state)
+                GameInfoBar(state, isDarkMode, { isDarkMode = it })
             Spacer(modifier = Modifier.height(12.dp))
             OpponentHands(state)
             Spacer(modifier = Modifier.height(12.dp))
@@ -417,12 +419,13 @@ fun UnoGameScreen(
             }
         )
     }
+    }
 }
 
 // region --- GameInfoBar ---
 
 @Composable
-private fun GameInfoBar(state: GameState) {
+private fun GameInfoBar(state: GameState, isDarkMode: Boolean, onDarkModeToggle: (Boolean) -> Unit) {
     val directionRotation by animateFloatAsState(
         targetValue = if (state.direction == GameDirection.CLOCKWISE) 0f else 180f,
         animationSpec = tween(500, easing = FastOutSlowInEasing),
@@ -462,6 +465,13 @@ private fun GameInfoBar(state: GameState) {
                     )
                 }
             }
+            // Dark mode toggle
+            IconButton(onClick = { onDarkModeToggle(!isDarkMode) }) {
+                Text(
+                    text = if (isDarkMode) "\u2600\uFE0F" else "\uD83C\uDF19",
+                    style = MaterialTheme.typography.bodyLarge
+                )
+            }
         }
     }
 }

shared/src/commonMain/kotlin/com/uno/shared/UnoTheme.kt

@@ -0,0 +1,57 @@
+package com.uno.shared
+
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material3.*
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.graphics.Color
+
+private val LightColorScheme = lightColorScheme(
+    primary = Color(0xFF1976D2),
+    onPrimary = Color.White,
+    primaryContainer = Color(0xFFBBDEFB),
+    onPrimaryContainer = Color(0xFF0D47A1),
+    secondary = Color(0xFFFF6D00),
+    onSecondary = Color.White,
+    secondaryContainer = Color(0xFFFFE0B2),
+    onSecondaryContainer = Color(0xFFE65100),
+    background = Color(0xFFF5F5F5),
+    onBackground = Color(0xFF1C1B1F),
+    surface = Color.White,
+    onSurface = Color(0xFF1C1B1F),
+    surfaceVariant = Color(0xFFE7E0EC),
+    onSurfaceVariant = Color(0xFF49454F),
+    error = Color(0xFFE53935),
+    onError = Color.White,
+)
+
+private val DarkColorScheme = darkColorScheme(
+    primary = Color(0xFF90CAF9),
+    onPrimary = Color(0xFF0D47A1),
+    primaryContainer = Color(0xFF1565C0),
+    onPrimaryContainer = Color(0xFFBBDEFB),
+    secondary = Color(0xFFFFB74D),
+    onSecondary = Color(0xFF3E2723),
+    secondaryContainer = Color(0xFFE65100),
+    onSecondaryContainer = Color(0xFFFFE0B2),
+    background = Color(0xFF121212),
+    onBackground = Color(0xFFE6E1E5),
+    surface = Color(0xFF1E1E1E),
+    onSurface = Color(0xFFE6E1E5),
+    surfaceVariant = Color(0xFF2C2C2C),
+    onSurfaceVariant = Color(0xFFCAC4D0),
+    error = Color(0xFFEF5350),
+    onError = Color(0xFF601010),
+)
+
+@Composable
+fun UnoTheme(
+    darkTheme: Boolean = isSystemInDarkTheme(),
+    content: @Composable () -> Unit
+) {
+    val colorScheme = if (darkTheme) DarkColorScheme else LightColorScheme
+
+    MaterialTheme(
+        colorScheme = colorScheme,
+        content = content
+    )
+}

webApp/src/wasmJsMain/kotlin/com/uno/web/Main.kt

@@ -4,26 +4,25 @@ import androidx.compose.foundation.layout.*
 import androidx.compose.material3.*
 import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
+import androidx.compose.ui.ExperimentalComposeUiApi
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.window.CanvasBasedWindow
 import com.uno.game.GameEngine
 import com.uno.game.model.*
 import com.uno.shared.UnoGameScreen
-import kotlinx.browser.document
+import com.uno.shared.UnoTheme
 import kotlinx.coroutines.delay
-import org.w3c.dom.HTMLElement
 
+@OptIn(ExperimentalComposeUiApi::class)
 fun main() {
-    val root = document.getElementById("root") as HTMLElement
-    root.innerHTML = ""
-    val container = document.createElement("div")
-    container.id = "app"
-    root.appendChild(container)
-    composeWebRoot()
+    CanvasBasedWindow(canvasElementId = "ComposeTarget") {
+        UnoApp()
+    }
 }
 
 @Composable
-fun composeWebRoot() {
+fun UnoApp() {
     val engine = remember { GameEngine() }
     var gameState by remember { mutableStateOf(engine.startGame()) }
     var gameStarted by remember { mutableStateOf(false) }
@@ -45,6 +44,7 @@ fun composeWebRoot() {
         }
     }
 
+    UnoTheme {
         if (!gameStarted) {
             WebStartScreen(onStartGame = { playerCount ->
                 gameState = engine.startGame(playerCount)
@@ -72,6 +72,7 @@ fun composeWebRoot() {
                 )
             }
         }
+    }
 }
 
 @Composable