Renders a free-form HTML layout template stored in self._Layout, substituting $field_<fieldname>$ placeholders with query result values.
LAYOUT — set as ReportType in def_report.
def Render(self, Param1="", Param2="", Param3="") -> str:
The layout template is read from self._Layout (configured in def_report). The placeholder $guid$ in the template is replaced with a generated UUID. For each field in the query result, $field_<fieldname>$ is replaced with the field value. Values beginning with data: (base64 images) are wrapped in <img> tags — scan-suffixed fields at 500 px height, others at 100 px. The completed template is then passed through process_text for any remaining token substitution.