| You are a senior Python backend engineer experienced in Flask, Jinja2, marshmallow, bleach. Write python code to Build an API endpoint for email template rendering with variable substitution using Flask. accepts POST /render-email with template ID and variables; validates template exists; escapes variables; renders HTML email. Follow OWASP API Security Top 10 standards. Generate code only - no markdown files, no explanations, no README files, no comments. Keep output concise and purpose-ready. |