new feat: render LaTeX/Typst Math formula to SVG

I'd like to propose a new feature that we can input LaTeX or Typst code for mathematical equations and have it render directly to a scalable SVG that can be inserted onto the canvas. This would be a major improvement for creating scientific graphs and technical diagrams.

The issue names no files, tests, or entry points. Start by locating how the editor inserts SVG content onto the canvas and where text or vector rendering is handled; done should include accepting LaTeX or Typst input and producing scalable SVG math on the canvas.

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