refactor: 积分榜导入导出改为右上角三点菜单，支持文件导出导入

app/src/main/java/com/unogame/ui/screens/ScoreboardScreen.kt

@@ -3,7 +3,10 @@ package com.unogame.ui.screens
 import android.content.ClipData
 import android.content.ClipboardManager
 import android.content.Context
+import android.net.Uri
 import android.widget.Toast
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.horizontalScroll
@@ -43,8 +46,49 @@ fun ScoreboardScreen(onBack: () -> Unit) {
     var detailEntry by remember { mutableStateOf<ScoreEntry?>(null) }
     var showImportDialog by remember { mutableStateOf(false) }
     var importJson by remember { mutableStateOf("") }
+    var showMenu by remember { mutableStateOf(false) }
     val gson = remember { Gson() }
 
+    // Export file launcher
+    val exportLauncher = rememberLauncherForActivityResult(
+        ActivityResultContracts.CreateDocument("application/json")
+    ) { uri: Uri? ->
+        uri?.let {
+            try {
+                val json = gson.toJson(scores)
+                context.contentResolver.openOutputStream(it)?.use { out ->
+                    out.write(json.toByteArray())
+                }
+                Toast.makeText(context, "备份已导出", Toast.LENGTH_SHORT).show()
+            } catch (e: Exception) {
+                Toast.makeText(context, "导出失败: ${e.message}", Toast.LENGTH_LONG).show()
+            }
+        }
+    }
+
+    // Import file launcher
+    val importLauncher = rememberLauncherForActivityResult(
+        ActivityResultContracts.OpenDocument()
+    ) { uri: Uri? ->
+        uri?.let {
+            try {
+                val json = context.contentResolver.openInputStream(it)?.bufferedReader()?.readText() ?: ""
+                val imported = gson.fromJson(json, Array<ScoreEntry>::class.java)?.toList() ?: emptyList()
+                if (imported.isNotEmpty()) {
+                    val merged = (scores + imported).distinctBy { e -> "${e.name}_${e.mode}_${e.date}" }
+                        .sortedByDescending { e -> e.points }.take(50)
+                    Scoreboard.saveScores(context, merged)
+                    scores = merged
+                    Toast.makeText(context, "成功导入 ${imported.size} 条记录", Toast.LENGTH_SHORT).show()
+                } else {
+                    Toast.makeText(context, "文件中无有效数据", Toast.LENGTH_SHORT).show()
+                }
+            } catch (e: Exception) {
+                Toast.makeText(context, "导入失败: ${e.message}", Toast.LENGTH_LONG).show()
+            }
+        }
+    }
+
     val filtered = if (selectedFilter == "全部") scores
     else scores.filter { it.mode == selectedFilter }
 
@@ -57,42 +101,55 @@ fun ScoreboardScreen(onBack: () -> Unit) {
                 IconButton(onClick = onBack) {
                     Icon(Icons.Default.ArrowBack, "返回", tint = Color.White)
                 }
-                Text("积分排行榜", fontSize = 24.sp, fontWeight = FontWeight.Bold, color = Color.White)
+                Text("积分排行榜", fontSize = 24.sp, fontWeight = FontWeight.Bold, color = Color.White, modifier = Modifier.weight(1f))
+                Box {
+                    IconButton(onClick = { showMenu = true }) {
+                        Icon(Icons.Default.MoreVert, "菜单", tint = Color.White)
                     }
-
+                    DropdownMenu(
-            Spacer(modifier = Modifier.height(16.dp))
+                        expanded = showMenu,
-
+                        onDismissRequest = { showMenu = false }
-            // Import / Export buttons
-            Row(
-                modifier = Modifier.fillMaxWidth(),
-                horizontalArrangement = Arrangement.spacedBy(8.dp)
                     ) {
-                OutlinedButton(
+                        DropdownMenuItem(
+                            text = { Text("导出到文件") },
                             onClick = {
+                                showMenu = false
+                                exportLauncher.launch("uno_scoreboard_backup.json")
+                            },
+                            leadingIcon = { Icon(Icons.Default.FileUpload, null) }
+                        )
+                        DropdownMenuItem(
+                            text = { Text("从文件导入") },
+                            onClick = {
+                                showMenu = false
+                                importLauncher.launch(arrayOf("application/json", "*/*"))
+                            },
+                            leadingIcon = { Icon(Icons.Default.FileDownload, null) }
+                        )
+                        DropdownMenuItem(
+                            text = { Text("复制备份") },
+                            onClick = {
+                                showMenu = false
                                 val json = gson.toJson(scores)
                                 val clipboard = context.getSystemService(Context.CLIPBOARD_SERVICE) as ClipboardManager
                                 clipboard.setPrimaryClip(ClipData.newPlainText("uno_scoreboard", json))
-                        Toast.makeText(context, "已复制备份JSON到剪贴板", Toast.LENGTH_SHORT).show()
+                                Toast.makeText(context, "已复制JSON到剪贴板", Toast.LENGTH_SHORT).show()
                             },
-                    modifier = Modifier.weight(1f),
+                            leadingIcon = { Icon(Icons.Default.ContentCopy, null) }
-                    colors = ButtonDefaults.outlinedButtonColors(contentColor = Color.White.copy(alpha = 0.7f))
+                        )
-                ) {
+                        DropdownMenuItem(
-                    Icon(Icons.Default.FileUpload, null, modifier = Modifier.size(16.dp))
+                            text = { Text("粘贴导入") },
-                    Spacer(modifier = Modifier.width(4.dp))
+                            onClick = {
-                    Text("导出备份", fontSize = 12.sp)
+                                showMenu = false
+                                showImportDialog = true
+                            },
+                            leadingIcon = { Icon(Icons.Default.ContentPaste, null) }
+                        )
                     }
-                OutlinedButton(
-                    onClick = { showImportDialog = true },
-                    modifier = Modifier.weight(1f),
-                    colors = ButtonDefaults.outlinedButtonColors(contentColor = Color.White.copy(alpha = 0.7f))
-                ) {
-                    Icon(Icons.Default.FileDownload, null, modifier = Modifier.size(16.dp))
-                    Spacer(modifier = Modifier.width(4.dp))
-                    Text("导入备份", fontSize = 12.sp)
                 }
             }
 
-            Spacer(modifier = Modifier.height(12.dp))
+            Spacer(modifier = Modifier.height(16.dp))
 
             // Mode filter chips
             if (scores.isNotEmpty()) {
@@ -282,7 +339,7 @@ fun ScoreboardScreen(onBack: () -> Unit) {
     if (showImportDialog) {
         AlertDialog(
             onDismissRequest = { showImportDialog = false },
-            title = { Text("导入备份", color = GoldAccent) },
+            title = { Text("粘贴导入", color = GoldAccent) },
             text = {
                 Column {
                     Text("粘贴之前导出的JSON数据：", color = Color.White.copy(alpha = 0.7f), fontSize = 14.sp)