fix(storefront): create missing footer payment-icon assets

bootstrap.json's footer.paymentIcons referenced /assets/images/
mir-logo.svg, visa-logo.svg, mastercard-logo.svg - none of that
directory's files existed until the RC-02 placeholder fix, and these
three were still missing. Site-wide broken-image icons in every page
footer. Added neutral labeled-badge SVGs (not reproductions of the
actual trademarked logo artwork) at the exact referenced paths, plus
an onerror fallback on the footer <img> for defense in depth.

src/assets/images/mir-logo.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 40 28" role="img" aria-label="MIR">
+  <rect width="40" height="28" rx="4" fill="#0f754e"/>
+  <text x="20" y="18" text-anchor="middle" font-family="Arial, sans-serif" font-size="11" font-weight="700" fill="#ffffff">MIR</text>
+</svg>