fix: raise text-ink/50 contrast to WCAG AA across 8 files

Live Lighthouse audit of /konto found the same class of bug as the
prior checkout/cart commit, one shade lighter: text-ink/50 measures
3.08:1 against the cream background, under the 4.5:1 WCAG AA minimum
for normal-size text. Grepped for every other use of the same token
(login divider, language switcher, sold-out label, admin image-upload
status text, admin hint text) and bumped them all to text-ink/70
(5.61:1, same value used in the earlier checkout fix) for one
consistent, compliant muted-text shade. Verified: tsc clean, 151/151
tests pass, /konto Lighthouse accessibility 96 -> 100.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/app/newsletter-bestaetigt/page.tsx

@@ -44,7 +44,7 @@ export default async function NewsletterBestaetigtPage(props: PageProps<"/newsle
               {t.newsletterBestaetigtPage.discountText(NEWSLETTER_DISCOUNT_PERCENT)}{" "}
               <span className="font-medium">{NEWSLETTER_DISCOUNT_CODE}</span>
             </p>
-            <p className="mt-2 text-xs text-ink/50">{t.newsletterBestaetigtPage.discountCopyHint}</p>
+            <p className="mt-2 text-xs text-ink/70">{t.newsletterBestaetigtPage.discountCopyHint}</p>
           </div>
         ) : null}