Implement preferred audio languages feature: update site settings to include preferred audio languages, modify related data structures and API endpoints, and enhance media processing to select audio tracks based on user preferences. Update frontend components for managing and displaying these settings.

backend/src/TeleWave.Application/Settings/AppSettingsReader.cs

@@ -21,4 +21,20 @@ public static class AppSettingsReader
 
         return value is not null && bool.TryParse(value, out var parsed) ? parsed : defaultValue;
     }
+
+    public static async Task<string> GetStringSettingAsync(
+        this IAppDbContext db,
+        string key,
+        string defaultValue,
+        CancellationToken cancellationToken
+    )
+    {
+        var value = await db
+            .AppSettings.AsNoTracking()
+            .Where(s => s.Key == key)
+            .Select(s => s.Value)
+            .FirstOrDefaultAsync(cancellationToken);
+
+        return value ?? defaultValue;
+    }
 }

backend/src/TeleWave.Application/Settings/GetSiteSettings/GetSiteSettingsQueryHandler.cs

@@ -12,6 +12,7 @@ public sealed class GetSiteSettingsQueryHandler(ISiteSettings siteSettings)
     )
     {
         var registrationEnabled = await siteSettings.IsRegistrationEnabledAsync(cancellationToken);
-        return new SiteSettingsDto(registrationEnabled);
+        var preferredAudio = await siteSettings.GetPreferredAudioLanguagesAsync(cancellationToken);
+        return new SiteSettingsDto(registrationEnabled, preferredAudio);
     }
 }

backend/src/TeleWave.Application/Settings/SettingKeys.cs

@@ -5,4 +5,8 @@ public static class SettingKeys
 {
     /// <summary>Разрешена ли открытая регистрация пользователей (по умолчанию — нет).</summary>
     public const string RegistrationEnabled = "registration.enabled";
+
+    /// <summary>Предпочитаемые языки аудиодорожек при обработке, через запятую в порядке приоритета
+    /// (напр. «rus,eng»). При наличии дорожки с таким языком она выбирается первой; иначе — дефолт ffmpeg.</summary>
+    public const string PreferredAudioLanguages = "media.preferredAudioLanguages";
 }

backend/src/TeleWave.Application/Settings/SiteSettingsDto.cs

@@ -1,4 +1,4 @@
 namespace TeleWave.Application.Settings;
 
 /// <summary>Глобальные настройки сайта, управляемые администратором.</summary>
-public sealed record SiteSettingsDto(bool RegistrationEnabled);
+public sealed record SiteSettingsDto(bool RegistrationEnabled, string PreferredAudioLanguages);

backend/src/TeleWave.Application/Settings/UpdateSiteSettings/UpdateSiteSettingsCommand.cs

@@ -3,4 +3,5 @@ using TeleWave.Application.Common.Models;
 
 namespace TeleWave.Application.Settings.UpdateSiteSettings;
 
-public sealed record UpdateSiteSettingsCommand(bool RegistrationEnabled) : ICommand<Result>;
+public sealed record UpdateSiteSettingsCommand(bool RegistrationEnabled, string PreferredAudioLanguages)
+    : ICommand<Result>;

backend/src/TeleWave.Application/Settings/UpdateSiteSettings/UpdateSiteSettingsCommandHandler.cs

@@ -17,6 +17,14 @@ public sealed class UpdateSiteSettingsCommandHandler(ISiteSettings siteSettings)
             command.RegistrationEnabled,
             cancellationToken
         );
+        // Нормализуем список языков: без пробелов, в нижнем регистре, пустые отбрасываем.
+        var languages = string.Join(
+            ',',
+            (command.PreferredAudioLanguages ?? string.Empty)
+                .Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
+                .Select(x => x.ToLowerInvariant())
+        );
+        await siteSettings.SetPreferredAudioLanguagesAsync(languages, cancellationToken);
         return Result.Success();
     }
 }