fix locale, add stop button, auto-logout on 401, migrate login shadows

- EmptyHero date respects system locale instead of hardcoded German
- Stop button (red square) replaces send/call during streaming, cancels stream cleanly
- Auto-logout on HTTP 401 (expired token) routes to login instead of error banner
- LoginScreen migrated from Modifier.shadow to kaizenShadow (design system pillar 4)

app/src/main/java/dev/kaizen/app/auth/LoginScreen.kt

@@ -33,7 +33,6 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
-import androidx.compose.ui.draw.shadow
 import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.SolidColor
@@ -49,6 +48,8 @@ import dev.kaizen.app.chat.MeshBackground
 import dev.kaizen.app.net.DEFAULT_BASE_URL
 import dev.kaizen.app.net.LoginResult
 import dev.kaizen.app.net.SessionViewModel
+import dev.kaizen.app.ui.effect.KaizenShadows
+import dev.kaizen.app.ui.effect.kaizenShadow
 import dev.kaizen.app.ui.theme.LocalKaizenAccent
 import androidx.compose.ui.res.stringResource
 import dev.kaizen.app.R
@@ -181,7 +182,7 @@ private fun GlassField(
         Modifier
             .fillMaxWidth()
             .widthIn(max = 420.dp)
-            .shadow(elevation = 6.dp, shape = KaizenShapes.lg, clip = false)
+            .kaizenShadow(stack = KaizenShadows.level1, cornerRadius = 20.dp)
             .clip(KaizenShapes.lg)
             .background(glassBg)
             .border(1.2.dp, glassBorder, KaizenShapes.lg)
@@ -220,7 +221,7 @@ private fun SignInButton(enabled: Boolean, loading: Boolean, onClick: () -> Unit
             .fillMaxWidth()
             .widthIn(max = 420.dp)
             .heightIn(min = 54.dp)
-            .shadow(elevation = 8.dp, shape = KaizenShapes.lg, clip = false)
+            .kaizenShadow(stack = KaizenShadows.level2, cornerRadius = 20.dp)
             .clip(KaizenShapes.lg)
             .then(fill)
             .clickable(enabled = enabled, onClick = onClick)

app/src/main/java/dev/kaizen/app/chat/ChatComponents.kt

@@ -121,7 +121,7 @@ fun EmptyHero(userName: String, onPick: (String) -> Unit, modifier: Modifier = M
     val cs = MaterialTheme.colorScheme
     val now = remember { LocalDateTime.now() }
     val dateLine = remember {
-        now.format(DateTimeFormatter.ofPattern("EEE, d. MMMM · HH:mm", Locale.GERMAN))
+        now.format(DateTimeFormatter.ofPattern("EEE, d. MMMM · HH:mm", Locale.getDefault()))
     }
 
     Column(
@@ -525,6 +525,8 @@ fun ChatInput(
     onValueChange: (String) -> Unit,
     onSend: () -> Unit,
     enabled: Boolean,
+    isStreaming: Boolean = false,
+    onStop: () -> Unit = {},
     pendingFiles: List<PendingFile> = emptyList(),
     onAddClick: () -> Unit = {},
     onRemoveFile: (String) -> Unit = {},
@@ -590,7 +592,9 @@ fun ChatInput(
 
                 Spacer(Modifier.weight(1f))
 
-                if (hasContent) {
+                if (isStreaming) {
+                    StopButton(onClick = onStop)
+                } else if (hasContent) {
                     SendButton(enabled = canSend, onClick = onSend)
                 } else {
                     CallButton(onClick = { /* TODO: call feature */ })
@@ -702,6 +706,26 @@ private fun CallButton(onClick: () -> Unit) {
     }
 }
 
+@Composable
+private fun StopButton(onClick: () -> Unit) {
+    val isDark = isSystemInDarkTheme()
+    val interaction = remember { MutableInteractionSource() }
+    val pressed by interaction.collectIsPressedAsState()
+    val pressScale by animateFloatAsState(if (pressed) 0.88f else 1f, label = "stop")
+
+    Box(
+        Modifier
+            .size(38.dp)
+            .scale(pressScale)
+            .clip(KaizenShapes.circle)
+            .background(Color(0xFFEF4444).copy(alpha = if (isDark) 0.85f else 0.80f))
+            .clickable(interactionSource = interaction, indication = null, onClick = onClick),
+        contentAlignment = Alignment.Center,
+    ) {
+        Icon(KaizenIcons.Square, stringResource(R.string.chat_stop), tint = Color.White, modifier = Modifier.size(16.dp))
+    }
+}
+
 // ── Attachment rendering ────────────────────────────────────────────────────
 
 private object NetworkImageCache {

app/src/main/java/dev/kaizen/app/chat/ChatScreen.kt

@@ -82,6 +82,7 @@ import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
 import androidx.lifecycle.compose.LifecycleResumeEffect
+import kotlinx.coroutines.Job
 import kotlinx.coroutines.async
 import kotlinx.coroutines.launch
 import java.io.ByteArrayOutputStream
@@ -108,6 +109,7 @@ fun ChatScreen(
     var samplingPrefs by remember { mutableStateOf(SamplingPrefs()) }
     var usedTokens by remember { mutableStateOf(0) }
     var chatModel by remember { mutableStateOf<String?>(null) }
+    var streamJob by remember { mutableStateOf<Job?>(null) }
 
     // Navigation State
     var currentScreen by remember { mutableStateOf(AppScreen.Chat) }
@@ -199,7 +201,10 @@ fun ChatScreen(
                 models = r.data
                 if (r.data.isNotEmpty()) session.store.saveModelsCache(r.data)
             }
-            is FetchResult.Fail -> errors.add(r.reason)
+            is FetchResult.Fail -> {
+                if ("HTTP 401" in r.reason) { session.logout(); return@LaunchedEffect }
+                errors.add(r.reason)
+            }
         }
         KaizenApi.fetchMe(cfg.baseUrl, cfg.token)?.let { me ->
             me.name?.let { settingsViewModel.updateUserName(it) }
@@ -395,7 +400,7 @@ fun ChatScreen(
             .filter { it.id != assistantId }
             .map { WireMessage(if (it.role == Role.User) "user" else "assistant", it.content) }
 
-        scope.launch {
+        streamJob = scope.launch {
             haptics.thinkingStart()
             var sawContent = false
             try {
@@ -490,7 +495,12 @@ fun ChatScreen(
                 }
             } catch (e: Exception) {
                 val idx = messages.indexOfLast { it.id == assistantId }
-                if (idx >= 0) {
+                if (e is kotlinx.coroutines.CancellationException) {
+                    if (idx >= 0) messages[idx] = messages[idx].copy(streaming = false, thinking = false)
+                } else if (e is ChatHttpException && e.code == 401) {
+                    if (idx >= 0) messages[idx] = messages[idx].copy(streaming = false, thinking = false)
+                    session.logout()
+                } else if (idx >= 0) {
                     val existing = messages[idx].content
                     val errorSuffix = "\n\n⚠ ${chatErrorText(e, context)}"
                     messages[idx] = messages[idx].copy(
@@ -501,6 +511,7 @@ fun ChatScreen(
                 }
             } finally {
                 isStreaming = false
+                streamJob = null
                 haptics.responseEnd()
             }
         }
@@ -845,6 +856,8 @@ fun ChatScreen(
                                 onValueChange = { input = it },
                                 onSend = { send(input) },
                                 enabled = !isStreaming,
+                                isStreaming = isStreaming,
+                                onStop = { streamJob?.cancel() },
                                 pendingFiles = pendingFiles,
                                 onAddClick = { showAttachMenu = !showAttachMenu },
                                 onRemoveFile = { id -> pendingFiles.removeAll { it.id == id } },

app/src/main/res/values-en/strings.xml

@@ -18,6 +18,7 @@
     <string name="chat_remove">Remove</string>
     <string name="chat_error">Error</string>
     <string name="chat_open_menu">Open menu</string>
+    <string name="chat_stop">Stop response</string>
     <string name="attach_camera">Take Photo</string>
     <string name="attach_gallery">Photo &amp; Video</string>
     <string name="attach_file">Choose File</string>

app/src/main/res/values/strings.xml

@@ -20,6 +20,7 @@
     <string name="chat_remove">Entfernen</string>
     <string name="chat_error">Fehler</string>
     <string name="chat_open_menu">Menü öffnen</string>
+    <string name="chat_stop">Antwort stoppen</string>
     <string name="attach_camera">Foto aufnehmen</string>
     <string name="attach_gallery">Foto &amp; Video</string>
     <string name="attach_file">Datei auswählen</string>