feat: 引入共享会话状态与未登录占位组件

core/designsystem/src/main/kotlin/com/mingyuan/android_client/core/designsystem/component/StateViews.kt

@@ -1,9 +1,11 @@
 package com.mingyuan.android_client.core.designsystem.component
 
 import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 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
@@ -21,6 +23,7 @@ import com.mingyuan.android_client.core.designsystem.theme.ErrorBackground
 import com.mingyuan.android_client.core.designsystem.theme.FaintText
 import com.mingyuan.android_client.core.designsystem.theme.MutedText
 import com.mingyuan.android_client.core.designsystem.theme.NeutralChip
+import com.mingyuan.android_client.core.designsystem.theme.PrimaryText
 
 @Composable
 fun EmptyState(
@@ -65,3 +68,30 @@ fun ErrorState(
         MingyuanButton(text = "重新加载", onClick = onRetry)
     }
 }
+
+@Composable
+fun LoggedOutState(
+    onLogin: (() -> Unit)? = null,
+    modifier: Modifier = Modifier,
+) {
+    Column(
+        modifier = modifier.fillMaxSize(),
+        verticalArrangement = Arrangement.Center,
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        Box(
+            modifier = Modifier.size(72.dp).background(NeutralChip, CircleShape),
+            contentAlignment = Alignment.Center,
+        ) {
+            Text("🔒", fontSize = 32.sp)
+        }
+        Spacer(Modifier.height(12.dp))
+        Text("未登录", color = PrimaryText, fontSize = 15.sp, fontWeight = FontWeight.SemiBold)
+        Spacer(Modifier.height(4.dp))
+        Text("登录后即可查看", color = FaintText, fontSize = 13.sp)
+        if (onLogin != null) {
+            Spacer(Modifier.height(16.dp))
+            MingyuanButton(text = "登录", onClick = onLogin)
+        }
+    }
+}