fix(ui): preserve SVG tags in DOMPurify config for KaTeX math rendering

[zharinov]

Issue for this PR

Closes #25812

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

DOMPurify was stripping <svg> and <path> elements from KaTeX-rendered HTML. KaTeX renders \sqrt, \overrightarrow, \widehat, \widetilde, \overbrace, \underbrace as inline SVG — these were silently removed during sanitization, leaving the radicand visible but the radical symbol missing.

Added ADD_TAGS: ["svg", "path"] and the necessary SVG attributes (d, viewBox, preserveAspectRatio, xmlns) to the DOMPurify config.

How did you verify your code works?

Tested in desktop dev build:

$$\sqrt{x^2 + y^2}$$ $$\sqrt[4]{a^3 + b^3}$$ $$F(t) = \sqrt{t + 1} + \sqrt[7]{t^2 - 9}$$ $$\overrightarrow{AB}$$ $$\widehat{XYZ}$$ $$\widetilde{f(x)}$$ $$\overbrace{x_1 + x_2 + \cdots + x_n}^{n\text{ terms}}$$ $$\underbrace{a + a + \cdots + a}_{m\text{ times}}$$

All render correctly. DOMPurify still strips event handlers on SVG elements.

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[zharinov]