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/Countdown.tsx

@@ -1,7 +1,7 @@
 import React, { CSSProperties, useEffect, useState } from 'react';
 import { useNode, UserComponent } from '@craftjs/core';
 import { cssPropsToString } from '../../utils/style-helpers';
-import { escapeHtml, escapeAttr, scopeId } from '../../utils/escape';
+import { escapeHtml, escapeAttr, scopeId, cssValue } from '../../utils/escape';
 
 interface CountdownProps {
   targetDate?: string;
@@ -154,10 +154,12 @@ Countdown.craft = {
     targetDate = DEFAULT_TARGET,
     heading = 'Coming Soon',
     style = {},
-    digitColor = '#ffffff',
-    labelColor = 'rgba(255,255,255,0.7)',
     bgColor = '#18181b',
   } = props;
+  // Sanitized -- raw string-interpolation sinks in the heading/digit/label
+  // style attributes below.
+  const digitColor = cssValue(props.digitColor) || '#ffffff';
+  const labelColor = cssValue(props.labelColor) || 'rgba(255,255,255,0.7)';
 
   const sectionStyle = cssPropsToString({
     padding: '60px 20px',