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/PricingTable.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 } from '../../utils/escape';
+import { escapeHtml, escapeAttr, safeUrl, cssValue } from '../../utils/escape';
 
 interface PricingPlan {
   name: string;
@@ -225,7 +225,9 @@ PricingTable.craft = {
   });
   const idAttr = props.anchorId ? ` id="${escapeAttr(props.anchorId)}"` : '';
   const plans = props.plans || defaultPlans;
-  const featuredBg = props.featuredBg || '#3b82f6';
+  // Sanitized -- featuredBg is a raw string-interpolation sink below (drives
+  // cardBg/btnBg/btnColor, all raw-interpolated into style="...").
+  const featuredBg = cssValue(props.featuredBg) || '#3b82f6';
 
   const cards = plans.map((plan) => {
     const cardBg = plan.isFeatured ? featuredBg : '#ffffff';