feat(webview): 添加blob下载功能并完善存储权限处理

- 添加pendingBlobDownload状态管理blob下载请求
- 实现API 30+系统上MANAGE_EXTERNAL_STORAGE权限检查
- 添加blob数据解码和文件保存功能
- 集成下载完成事件分发机制
- 完善存储权限对话框中的状态清理逻辑
- 实现blob下载成功后的相册保存或文件打开操作

sdk-webview/src/main/java/com/xuqm/sdk/webview/XWebViewView.kt

@@ -231,6 +231,8 @@ fun XWebViewView(
     var showImageSourceDialog by remember { mutableStateOf(false) }
     var showStoragePermissionDialog by remember { mutableStateOf(false) }
     val pendingUrlDownload = remember { mutableStateOf<Pair<String, String?>?>(null) }
+    // blobdownload pending: (url, filename, base64Data)
+    val pendingBlobDownload = remember { mutableStateOf<Triple<String, String, String>?>(null) }
 
     val notificationPermissionLauncher = rememberLauncherForActivityResult(
         ActivityResultContracts.RequestPermission()
@@ -304,6 +306,15 @@ fun XWebViewView(
                     android.util.Log.e("XWV", "blobdownload: empty data")
                     return@handler
                 }
+                // On API 30+, writing to public Downloads requires MANAGE_EXTERNAL_STORAGE.
+                if (config.downloadDestination == FileDownloadDestination.PublicDownloads &&
+                    Build.VERSION.SDK_INT >= Build.VERSION_CODES.R &&
+                    !FileSDK.isManageStorageGranted(context)
+                ) {
+                    pendingBlobDownload.value = Triple(url, filename, b64)
+                    showStoragePermissionDialog = true
+                    return@handler
+                }
                 android.util.Log.d("XWV", "blobdownload: filename=$filename, b64Len=${b64.length}, dest=${config.downloadDestination}")
                 coroutineScope.launch(Dispatchers.IO) {
                     runCatching {
@@ -402,6 +413,7 @@ fun XWebViewView(
         val observer = LifecycleEventObserver { _, event ->
             if (event == Lifecycle.Event.ON_RESUME) {
                 val pd = pendingUrlDownload.value
+                val pbd = pendingBlobDownload.value
                 if (pd != null && FileSDK.isManageStorageGranted(context)) {
                     val (url, filename) = pd
                     pendingUrlDownload.value = null
@@ -436,6 +448,27 @@ fun XWebViewView(
                         }
                     }
                 }
+                if (pbd != null && FileSDK.isManageStorageGranted(context)) {
+                    val (url, filename, b64) = pbd
+                    pendingBlobDownload.value = null
+                    coroutineScope.launch(Dispatchers.IO) {
+                        runCatching {
+                            FileSDK.saveBlobDownload(context, b64, filename, config.downloadDestination)
+                        }.onSuccess { file ->
+                            android.util.Log.d("XWV", "blobdownload saved: ${file.absolutePath}, size=${file.length()}")
+                            val savedToGallery = runCatching { FileSDK.saveImageToGallery(context, file) }.getOrDefault(false)
+                            withContext(Dispatchers.Main) {
+                                dispatchDownloadEvent("__xwvDownloadDone", url, ",success:true")
+                                if (!savedToGallery) FileSDK.openFile(context, file)
+                            }
+                        }.onFailure { e ->
+                            android.util.Log.e("XWV", "blobdownload FAILED", e)
+                            withContext(Dispatchers.Main) {
+                                dispatchDownloadEvent("__xwvDownloadDone", url, ",success:false,error:'${e.message?.escapeJs()}'")
+                            }
+                        }
+                    }
+                }
             }
         }
         lifecycleOwner.lifecycle.addObserver(observer)
@@ -564,6 +597,7 @@ fun XWebViewView(
             onDismissRequest = {
                 showStoragePermissionDialog = false
                 pendingUrlDownload.value = null
+                pendingBlobDownload.value = null
             },
             title = { Text("需要存储权限") },
             text = { Text("下载文件需要「所有文件访问权限」，请在设置中授权后将自动继续下载。") },
@@ -577,6 +611,7 @@ fun XWebViewView(
                 TextButton(onClick = {
                     showStoragePermissionDialog = false
                     pendingUrlDownload.value = null
+                    pendingBlobDownload.value = null
                 }) { Text("取消") }
             },
         )