fix(app): 修复视频播放明文HTTP与双网络访问切换

lib/core/config/app_config.dart

@@ -15,6 +15,9 @@ class AppConfig {
   /// `ipconfig getifaddr en0` 重新确认。默认值只改这一行。
   static const String devHostBaseUrl = 'http://192.168.31.187:8081';
 
+  /// 办公室内网（Wi-Fi）直连地址，双网络自动切换时的首选。
+  static const String lanBaseUrl = 'http://192.168.31.250:8081';
+
   static const String _loopbackBaseUrl = 'http://127.0.0.1:8081';
 
   static const String _overrideBaseUrl = String.fromEnvironment('API_BASE_URL');
@@ -59,6 +62,31 @@ class AppConfig {
 
   static const Duration requestTimeout = Duration(seconds: 8);
 
+  /// 探测内网地址是否可达，可达则切换为内网直连，否则回落到公网地址。
+  ///
+  /// Wi-Fi 下内网直连更快；移动数据下内网不可达，自动回落到公网端口映射。
+  static Future<void> probeAndApplyBaseUrl() async {
+    try {
+      final client = HttpClient()
+        ..connectionTimeout = const Duration(seconds: 2);
+      final request = await client.getUrl(
+        Uri.parse('$lanBaseUrl/app/categories'),
+      );
+      final response = await request.close().timeout(const Duration(seconds: 2));
+      await response.drain<void>();
+      client.close(force: true);
+      if (response.statusCode == 200) {
+        applyRuntimeBaseUrl(lanBaseUrl);
+        return;
+      }
+    } catch (_) {
+      // 内网不可达，回落到公网。
+    }
+    applyRuntimeBaseUrl(
+      compiledBaseUrl.isNotEmpty ? compiledBaseUrl : defaultBaseUrl,
+    );
+  }
+
   /// 后端返回的是相对路径（/files/...），这里补上服务地址。
   static String mediaUrl(String path) {
     if (path.isEmpty) return '';

lib/core/config/server_endpoint.dart

@@ -39,11 +39,11 @@ abstract final class ServerEndpoint {
   /// In release builds this returns immediately without reading preferences.
   static Future<void> load({
     bool debug = kDebugMode,
-    SharedPreferencesAsync? preferences,
+    SharedPreferences? preferences,
   }) async {
     if (!debug) return;
     try {
-      final prefs = preferences ?? SharedPreferencesAsync();
+      final prefs = preferences ?? await SharedPreferences.getInstance();
       final stored = await prefs.getString(preferenceKey);
       AppConfig.applyRuntimeBaseUrl(
         resolve(
@@ -60,12 +60,12 @@ abstract final class ServerEndpoint {
   /// Persists a normalized runtime endpoint.
   static Future<bool> save(
     String raw, {
-    SharedPreferencesAsync? preferences,
+    SharedPreferences? preferences,
   }) async {
     final normalized = normalize(raw);
     if (normalized == null) return false;
     try {
-      await (preferences ?? SharedPreferencesAsync()).setString(
+      await (preferences ?? await SharedPreferences.getInstance()).setString(
         preferenceKey,
         normalized,
       );
@@ -76,9 +76,9 @@ abstract final class ServerEndpoint {
   }
 
   /// Removes the persisted runtime endpoint.
-  static Future<void> clear({SharedPreferencesAsync? preferences}) async {
+  static Future<void> clear({SharedPreferences? preferences}) async {
     try {
-      await (preferences ?? SharedPreferencesAsync()).remove(preferenceKey);
+      await (preferences ?? await SharedPreferences.getInstance()).remove(preferenceKey);
     } catch (_) {
       // Clearing an optional developer override is best effort.
     }