Fix media downloading

DiscordChatExporter.Domain/Internal/PathEx.cs

@@ -14,5 +14,27 @@ namespace DiscordChatExporter.Domain.Internal
         }
 
         public static string EscapePath(string path) => EscapePath(new StringBuilder(path)).ToString();
+
+        public static string MakeUniqueFilePath(string baseFilePath, int maxAttempts = 100)
+        {
+            if (!File.Exists(baseFilePath))
+                return baseFilePath;
+
+            var baseDirPath = Path.GetDirectoryName(baseFilePath);
+            var baseFileNameWithoutExtension = Path.GetFileNameWithoutExtension(baseFilePath);
+            var baseFileExtension = Path.GetExtension(baseFilePath);
+
+            for (var i = 1; i <= maxAttempts; i++)
+            {
+                var filePath = $"{baseFileNameWithoutExtension} ({i}){baseFileExtension}";
+                if (!string.IsNullOrWhiteSpace(baseDirPath))
+                    filePath = Path.Combine(baseDirPath, filePath);
+
+                if (!File.Exists(filePath))
+                    return filePath;
+            }
+
+            return baseFilePath;
+        }
     }
 }