fix(log): input text visibility + space-in-date 502

- UnifiedQueryPanel: fix JS operator precedence — .replace(' ','T') was
  called on '.000Z' suffix instead of concatenated string, resulting in
  '2026-06-27 12:46:28.000Z' (space not replaced) → ES 502
- normalizeTime: add space→T fallback for backward compat
- SyntaxHighlightInput: fix z-index layering (textarea z=2 was covering
  pre z=1, making highlighted text invisible). Move bg/border to parent,
  textarea bg→transparent, pre above textarea

backend/controller/log_proxy.go

@@ -155,6 +155,8 @@ func (h *LogProxyHandler) QueryES(c *gin.Context) {
 				if s == "" {
 					return s
 				}
+				// 空格 → T（兼容前端未正确转换的格式）// Logan.Li
+				s = strings.Replace(s, " ", "T", 1)
 				// 查找时间部分结束位置（Z 或 +）
 				tzIdx := strings.IndexAny(s, "Z+")
 				timePart := s