security: add safeImageUrl, un-break M-5's over-blocking of image-context SVG data URIs

M-5 made safeUrl() block data:image/svg+xml everywhere, including the
image-only sinks (<img src>, CSS url()) that Gallery's default images and
other SVG placeholders rely on. Loaded as an image, an SVG is rasterized
and never executes an inline <script>/onload= -- that only happens when
it's navigated to or loaded as an <iframe> document -- so M-5 over-blocked
the safe contexts and broke every published Gallery (and other components
using an SVG placeholder) using safeUrl's default images in prod.

Adds safeImageUrl(): identical javascript:/vbscript: handling to safeUrl,
but treats data: as an allowlist of image/* subtypes instead of a
blocklist -- allows all data:image/* (including svg+xml, with or without
base64), still blocks data:text/html and any other non-image data: type.

Swapped to safeImageUrl at IMAGE-src / CSS-image url() sinks only:
- Gallery.tsx img src + lightbox data-lb-src
- ImageBlock.tsx img src (toHtml)
- Logo.tsx / Navbar.tsx logo <img> src (their href/link targets keep safeUrl)
- style-helpers.ts sanitizeCssValue's url(...) handling (background-image
  for HeroSimple/BackgroundSection/Section/CallToAction)

Left on safeUrl (href/iframe/form-action/navigation sinks, where
data:image/svg+xml must stay blocked): ButtonLink, Icon link, SocialLinks,
Menu/Navbar link hrefs, PricingTable buttonHref, _cta-helpers,
ContentSlider buttonHref, FeaturesGrid buttonUrl, FormContainer action
(via form-relay-wiring), MapEmbed/VideoBlock iframe src.

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

craft/src/utils/escape.ts

@@ -64,20 +64,7 @@ export function safeUrl(s: string): string {
   const trimmed = s.trim();
   if (trimmed === '') return '';
 
-  // Build a normalized copy for scheme detection only: decode numeric HTML
-  // entities (catches e.g. j -> 'j'), strip whitespace/control chars,
-  // and lowercase.
-  const normalized = decodeNumericEntities(trimmed)
-    .replace(/[\x00-\x20]+/g, '')
-    .toLowerCase();
-
-  // Strip any colons before matching the scheme prefix. This defeats
-  // obfuscation that splices extra colons into the scheme name itself
-  // (e.g. decoding : mid-word produces "java:script:alert(1)", which
-  // would otherwise dodge a literal "^javascript:" check) while still
-  // reliably catching the real "javascript:"/"vbscript:"/"data:text/html"
-  // prefixes once their own colon is removed.
-  const collapsed = normalized.replace(/:/g, '');
+  const collapsed = normalizeForSchemeCheck(trimmed);
 
   if (DANGEROUS_SCHEME_PREFIXES.some((prefix) => collapsed.startsWith(prefix))) {
     return '';
@@ -86,6 +73,61 @@ export function safeUrl(s: string): string {
   return trimmed;
 }
 
+/**
+ * Image-context variant of `safeUrl` for IMAGE sinks only (`<img src>`, CSS
+ * `url(...)` backgrounds). `data:image/svg+xml` is safe here -- loaded as an
+ * image, an SVG is rasterized and never executes an inline <script>/onload=
+ * the way it would as a navigation/iframe document -- so, unlike `safeUrl`,
+ * this ALLOWS every `data:image/*` subtype (svg+xml, png, jpeg, gif, webp,
+ * ..., with or without `;base64`).
+ *
+ * Still blocks `javascript:` / `vbscript:` (same obfuscation-resistant
+ * normalization as `safeUrl`), and -- because this is an image sink, not a
+ * general-purpose URL sink -- treats `data:` as an ALLOWLIST rather than a
+ * blocklist: any `data:` URI whose type is NOT `image/*` (`data:text/html`,
+ * `data:application/javascript`, `data:text/javascript`, etc.) is blocked
+ * too, since none of those are legitimate image sources.
+ *
+ * Do NOT use this for href/iframe/form-action/navigation sinks -- keep
+ * those on `safeUrl`, which still blocks `data:image/svg+xml`.
+ */
+export function safeImageUrl(s: unknown): string {
+  if (typeof s !== 'string') return '';
+
+  const trimmed = s.trim();
+  if (trimmed === '') return '';
+
+  const collapsed = normalizeForSchemeCheck(trimmed);
+
+  if (collapsed.startsWith('javascript') || collapsed.startsWith('vbscript')) {
+    return '';
+  }
+  if (collapsed.startsWith('data') && !collapsed.startsWith('dataimage')) {
+    // A data: URI whose MIME type isn't image/* -- e.g. data:text/html,
+    // data:application/javascript, data:text/javascript. No legitimate
+    // image source needs these; block unconditionally.
+    return '';
+  }
+
+  return trimmed;
+}
+
+// Normalizes a trimmed URL string for scheme-prefix matching only: decodes
+// numeric HTML entities (catches e.g. &#106; -> 'j'), strips whitespace /
+// control chars, lowercases, then strips every colon. Stripping colons
+// defeats obfuscation that splices extra colons into the scheme name itself
+// (e.g. decoding &#58; mid-word produces "java:script:alert(1)", which would
+// otherwise dodge a literal "^javascript:" check) while still reliably
+// catching the real "javascript:"/"vbscript:"/"data:..." prefixes once their
+// own colon is removed. Used for prefix `.startsWith()` checks only -- the
+// original (non-collapsed) string is always what gets returned/emitted.
+function normalizeForSchemeCheck(trimmed: string): string {
+  return decodeNumericEntities(trimmed)
+    .replace(/[\x00-\x20]+/g, '')
+    .toLowerCase()
+    .replace(/:/g, '');
+}
+
 /**
  * Neutralizes CSS-context breakout for a single design-token value (color,
  * length, gradient, etc.) so it is safe to interpolate RAW into either CSS