fix(builder): sanitize CSS-value sinks to prevent style/<style> breakout XSS

Adds a single cssValue() sanitizer (src/utils/escape.ts) that strips
<>{};"'\ and neutralizes url(), safe for both style="..." attribute and
<style>...</style> element contexts. Applies it at every raw user-prop
CSS-value interpolation sink found via grep across src/components (colors,
sizes, gaps interpolated directly into style strings/<style> blocks),
including the highest-risk <style>-context sinks: ColumnLayout gap,
Menu/Navbar hover and background colors. Also Number()-coerces the
`columns` grid-template-columns sinks in Gallery/Testimonials/NumberCounter
as defense in depth. Regression tests assert </style><script> payloads are
neutralized and normal colors still render.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/components/sections/Testimonials.tsx

@@ -1,7 +1,7 @@
 import React, { CSSProperties } from 'react';
 import { useNode, UserComponent } from '@craftjs/core';
 import { cssPropsToString } from '../../utils/style-helpers';
-import { escapeHtml, escapeAttr } from '../../utils/escape';
+import { escapeHtml, escapeAttr, cssValue } from '../../utils/escape';
 
 interface Testimonial {
   quote: string;
@@ -139,11 +139,16 @@ Testimonials.craft = {
   const {
     testimonials = defaultTestimonials,
     layout = 'grid',
-    columns = 3,
     style = {},
-    cardBg = '#f8fafc',
-    starColor = '#f59e0b',
   } = props;
+  // Number() coercion: `columns` is a raw string-interpolation sink into the
+  // grid style attribute below (repeat(${columns},1fr)); Number() of
+  // anything non-numeric collapses safely to NaN instead of breaking out.
+  const columns = Number(props.columns) || 3;
+  // Sanitized -- raw string-interpolation sinks below (cardCss / starsHtml
+  // style attributes).
+  const cardBg = cssValue(props.cardBg) || '#f8fafc';
+  const starColor = cssValue(props.starColor) || '#f59e0b';
 
   const items = testimonials.length > 0 ? testimonials : defaultTestimonials;