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/Gallery.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, safeUrl, scopeId } from '../../utils/escape';
+import { escapeHtml, escapeAttr, safeUrl, scopeId, cssValue } from '../../utils/escape';
 
 interface GalleryImage {
   src: string;
@@ -130,8 +130,14 @@ Gallery.craft = {
     ...props.style,
   });
   const images = props.images || defaultImages;
-  const columns = props.columns || 3;
-  const gap = props.gap || '16px';
+  // Number() coercion: `columns` is a raw string-interpolation sink into the
+  // grid style attribute below (repeat(${columns},1fr)) -- a non-numeric
+  // (e.g. hand-crafted/AI-generated tree) value would otherwise be able to
+  // break out; Number() of anything non-numeric collapses safely to NaN.
+  const columns = Number(props.columns) || 3;
+  // Sanitized -- gap is a raw string-interpolation sink into the grid style
+  // attribute below.
+  const gap = cssValue(props.gap) || '16px';
   const lightbox = props.lightbox || false;
 
   // Deterministic AND unique id, scoped on the Craft node id, for this