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/newsletter/components/WeeklyImpulsesHero.tsx

@@ -2,6 +2,17 @@ import Link from "next/link";
 import Image from "next/image";
 import { Reveal } from "../../components/Reveal";
 
+// Same lock icon + copy as /challenge's and the shared Newsletter
+// component's trust note — unified across all newsletter-signup forms.
+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>
+  );
+}
+
 const checklist = [
   "Jeden Mittwoch neue Impulse & Tipps",
   "Kurz & knackig – in 5 Minuten gelesen",
@@ -47,7 +58,7 @@ export function WeeklyImpulsesHero() {
           <div className="flex flex-col gap-6 items-start w-full flex-1 lg:justify-center">
             {/* Pill badge */}
             <div className="flex gap-2 items-center border border-border rounded-full pl-3.5 pr-4 py-2">
-              <img alt="" src="/icon-envelope-small.svg" className="w-4 h-3 shrink-0" />
+              <Image alt="" src="/icon-envelope-small.svg" width={16} height={12} className="w-4 h-3 shrink-0" />
               <span className="text-body-sm font-semibold text-text-primary whitespace-nowrap">
                 Jeden Mittwoch in deinem Postfach
               </span>
@@ -73,7 +84,7 @@ export function WeeklyImpulsesHero() {
             <ul className="flex flex-col gap-3 items-start w-full">
               {checklist.map((item) => (
                 <li key={item} className="flex gap-[0.625rem] items-center w-full">
-                  <img alt="" src="/icon-check.svg" className="size-5 shrink-0" />
+                  <Image alt="" src="/icon-check.svg" width={20} height={20} className="size-5 shrink-0" />
                   <span className="flex-1 text-body text-text-primary">{item}</span>
                 </li>
               ))}
@@ -96,9 +107,31 @@ export function WeeklyImpulsesHero() {
               </button>
             </div>
 
+            {/* Consent checkbox — this signup's legal basis is consent
+                (email marketing), same wording/pattern as the shared
+                Newsletter component's and 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>
+
             <div className="flex gap-[0.375rem] items-center">
-              <img alt="" src="/icon-lock.svg" className="size-3.5" />
-              <span className="text-label text-text-muted">Keine Werbung. Jederzeit abbestellbar.</span>
+              <LockIcon />
+              <span className="text-label text-[#888]">Keine Werbung. Jederzeit abbestellbar.</span>
             </div>
           </div>
         </Reveal>