🎨 Palette: [UX improvement] Add aria-hidden to decorative SVGs (#70)

* Added aria-hidden="true" to decorative SVG icons within interactive elements (buttons, links) in Lightbox, ThemeToggle, Footer, BackLink, and MapView.
* Added role="alert" and aria-live="polite" to the MapView loading indicator.
* Documented learning in .Jules/palette.md

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

components/Footer.tsx

@@ -40,6 +40,7 @@ export function Footer() {
               aria-label="Instagram"
             >
               <svg
+                aria-hidden="true"
                 width="16"
                 height="16"
                 viewBox="0 0 24 24"
@@ -58,6 +59,7 @@ export function Footer() {
           {footer?.email && (
             <a href={`mailto:${footer.email}`} className="footer__link" aria-label="Email">
               <svg
+                aria-hidden="true"
                 width="16"
                 height="16"
                 viewBox="0 0 24 24"
@@ -81,6 +83,7 @@ export function Footer() {
               aria-label="Website"
             >
               <svg
+                aria-hidden="true"
                 width="16"
                 height="16"
                 viewBox="0 0 24 24"