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/NewsletterModal.tsx

@@ -2,6 +2,7 @@
 
 import { useEffect, useRef } from "react";
 import Image from "next/image";
+import Link from "next/link";
 import { AnimatePresence, motion } from "motion/react";
 
 const features = [
@@ -149,7 +150,7 @@ export function NewsletterModal({ open, onClose }: { open: boolean; onClose: ()
           aria-label="Schließen"
           className="absolute top-6 right-6 z-10 size-6 flex items-center justify-center active:scale-90 transition-transform"
         >
-          <img alt="" src="/icon-close.png" className="size-full object-contain" />
+          <Image alt="" src="/icon-close.png" width={24} height={24} className="size-full object-contain" />
         </button>
 
         {/* modal-top: photo + copy/form, stacked below md */}
@@ -170,7 +171,7 @@ export function NewsletterModal({ open, onClose }: { open: boolean; onClose: ()
                 uses this exact same asset); without it the icon renders
                 flipped. */}
             <div className="w-16 h-14 -rotate-4 -scale-y-100">
-              <img alt="" src="/newsletter-icon.svg" className="w-full h-full" />
+              <Image alt="" src="/newsletter-icon.svg" width={64} height={56} className="w-full h-full" />
             </div>
 
             <p
@@ -205,7 +206,16 @@ export function NewsletterModal({ open, onClose }: { open: boolean; onClose: ()
                   className="size-4 shrink-0 rounded-xs border border-border accent-brand"
                 />
                 <span className="text-label text-text-primary">
-                  Ich akzeptiere die Datenschutzerklärung.
+                  Ich akzeptiere die{" "}
+                  <Link
+                    href="/datenschutz"
+                    target="_blank"
+                    rel="noopener noreferrer"
+                    className="underline hover:text-brand"
+                  >
+                    Datenschutzerklärung
+                  </Link>
+                  .
                 </span>
               </label>
             </form>
@@ -224,8 +234,8 @@ export function NewsletterModal({ open, onClose }: { open: boolean; onClose: ()
         <div className="flex flex-col md:flex-row items-start px-8 md:px-20 py-6 md:py-9 gap-8 md:gap-6">
           {features.map((f) => (
             <div key={f.title} className="flex-1 flex gap-6 items-start w-full">
-              <div className="h-10 w-10 shrink-0 flex items-center justify-center">
-                <img alt="" src={f.icon} className="max-h-10 max-w-10 object-contain" />
+              <div className="relative h-10 w-10 shrink-0 flex items-center justify-center">
+                <Image alt="" src={f.icon} fill sizes="40px" className="object-contain" />
               </div>
               <div className="flex flex-col gap-3 items-start flex-1 min-w-0">
                 <p