fix(app): 对齐 release 修复（播放明文HTTP、shared_preferences 降级防崩溃、双网络访问）

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.
     }