feat(kling): add validation error display in timeline panel and update UI components

- Remove unused audio base64 reference and error message in VoiceSelector
- Rename CSS class from 'result-banner' to 'result-inline' and update button styling
- Pass validationError prop from GenerateStep to TimelinePanel
- Add validation error display in TimelinePanel with error state styling
- Update conditional rendering to show either validation error or duration diff
- Add CloseCircleOutlined icon for error status display

yudao-module-tik/src/main/java/cn/iocoder/yudao/module/tik/voice/service/TikUserVoiceServiceImpl.java

@@ -580,43 +580,6 @@ public class TikUserVoiceServiceImpl implements TikUserVoiceService {
                 StrUtil.blankToDefault(requestFormat, getDefaultFormat()));
     }
 
-    private String buildFileName(String voiceId, String format) {
-        String safeVoice = StrUtil.blankToDefault(voiceId, "voice")
-                .replaceAll("[^a-zA-Z0-9_-]", "");
-        return safeVoice + "-" + System.currentTimeMillis() + "." + format;
-    }
-
-    private String resolveContentType(String format) {
-        if (format == null) {
-            return "audio/mpeg";
-        }
-        return switch (format.toLowerCase()) {
-            case "wav" -> "audio/wav";
-            case "flac" -> "audio/flac";
-            default -> "audio/mpeg";
-        };
-    }
-
-    private String determineSynthesisText(String transcriptionText, String inputText, boolean allowFallback) {
-        StringBuilder builder = new StringBuilder();
-        if (StrUtil.isNotBlank(transcriptionText)) {
-            builder.append(transcriptionText.trim());
-        }
-        if (StrUtil.isNotBlank(inputText)) {
-            if (builder.length() > 0) {
-                builder.append("\n");
-            }
-            builder.append(inputText.trim());
-        }
-        if (builder.length() > 0) {
-            return builder.toString();
-        }
-        if (allowFallback) {
-            return getPreviewText();
-        }
-        throw exception(VOICE_TTS_FAILED, "请提供需要合成的文本内容");
-    }
-
     /**
      * 从URL中提取原始URL（去除查询参数和锚点）
      */