feat(newsletter, checkout): add consent links, unify trust-note styling, optimize images

Every email-signup form (Home/newsletter Newsletter section, /newsletter
hero, /challenge, the Newsletter overlay) now links "Datenschutzerklärung"
to /datenschutz next to its consent checkbox, opened in a new tab so a
partially filled form isn't lost. Checkout gets an equivalent AGB +
Datenschutzerklärung note under the order button, and the Versand
modal's Widerrufsbelehrung link also opens in a new tab.

Unified the "Keine Werbung. Jederzeit abbestellbar." trust note (icon +
#888 copy) across all newsletter forms, matching /challenge's existing
style instead of each form having its own wording/color.

Also converted the remaining raw <img> tags in these files to next/image
per the no-img-element lint rule (bandwidth/LCP).

app/components/Newsletter.tsx

@@ -1,6 +1,20 @@
 import type { ReactNode } from "react";
+import Link from "next/link";
+import Image from "next/image";
 import { Reveal } from "./Reveal";
 
+// Same lock icon + copy as /challenge's and /newsletter's EmailCapture —
+// unified across all newsletter-signup forms instead of each having its
+// own wording/color for this trust note.
+function LockIcon() {
+  return (
+    <svg width="14" height="14" viewBox="0 0 14 14" fill="none" className="shrink-0">
+      <rect x="2" y="6" width="10" height="7" rx="1.5" stroke="#888" strokeWidth="1.3" />
+      <path d="M4.5 6V4.5a2.5 2.5 0 0 1 5 0V6" stroke="#888" strokeWidth="1.3" />
+    </svg>
+  );
+}
+
 type NewsletterProps = {
   title?: ReactNode;
   description?: string;
@@ -32,9 +46,11 @@ export function Newsletter({
             {/* Decorative envelope icon, tilted -4° as per design */}
             <div className="flex items-center justify-center shrink-0 w-[4.23rem] h-[3.71rem]">
               <div className="-rotate-4 -scale-y-100">
-                <img
+                <Image
                   alt=""
                   src="/newsletter-icon.svg"
+                  width={64}
+                  height={55}
                   className="w-16 h-[3.438rem] block"
                 />
               </div>
@@ -73,9 +89,34 @@ export function Newsletter({
                 </button>
               </div>
 
-              {/* Privacy note */}
-              <p className="text-label text-text-primary font-normal leading-normal">
-                Ich achte auf deine Daten. Kein Spam, jederzeit abbestellbar.
+              {/* Consent checkbox — required since this signup's legal
+                  basis is consent (email marketing), not the "Ich achte
+                  auf deine Daten" trust note alone. Same wording/pattern
+                  as NewsletterModal's checkbox. */}
+              <label className="flex gap-2 items-start cursor-pointer">
+                <input
+                  type="checkbox"
+                  className="size-4 shrink-0 mt-0.5 rounded-xs border border-border accent-brand"
+                />
+                <span className="text-label text-text-primary font-normal leading-normal">
+                  Ich akzeptiere die{" "}
+                  <Link
+                    href="/datenschutz"
+                    target="_blank"
+                    rel="noopener noreferrer"
+                    className="underline hover:text-brand"
+                  >
+                    Datenschutzerklärung
+                  </Link>
+                  .
+                </span>
+              </label>
+
+              {/* Privacy note — same icon/copy/color as the other
+                  newsletter forms (see /challenge's EmailCapture). */}
+              <p className="flex items-center gap-1.5 text-label text-[#888] font-normal leading-normal">
+                <LockIcon />
+                Keine Werbung. Jederzeit abbestellbar.
               </p>
 
             </div>