Add persistent account navigation (sidebar/tabs); fix CTA arrow on Android

Konto-Aktionen links (profile, wishlist, logout) used to live at the bottom of the orders page's own content — unreachable once the order list got long enough. New KontoShell + AccountNav give every /konto/* page a persistent sidebar (sm+) / tab bar (mobile) instead, always reachable regardless of list length. The order filters also collapse behind a "Filter" toggle on mobile now, since the tab bar above them left little room for 3 full-width dropdowns.

Also: replaced the Unicode "→" arrow in CTA links (Tools.tsx, Blog.tsx, ProductGrid.tsx) with an SVG icon — the glyph isn't covered by the site's custom fonts, so browsers fall back to a system font per-platform; confirmed sitting visibly low relative to the label text on Android/Chrome (Galaxy S22), not reproducible in desktop Chromium. An SVG has no font-fallback path, so it renders identically everywhere.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/components/Blog.tsx

@@ -2,6 +2,7 @@ import Link from "next/link";
 import Image from "next/image";
 import { getBlogPosts } from "../lib/payload";
 import { Reveal, RevealGroup, RevealItem } from "./Reveal";
+import { ArrowRightIcon } from "./ArrowRightIcon";
 
 export async function Blog() {
   const posts = await getBlogPosts(3);
@@ -69,7 +70,7 @@ export async function Blog() {
               href={featured.href}
               className="flex items-center gap-1 font-bold text-body text-text-primary whitespace-nowrap hover:text-brand transition-colors"
             >
-              <span aria-hidden>→</span>
+              <ArrowRightIcon />
               <span>Zum Beitrag</span>
             </Link>
           </div>
@@ -122,7 +123,7 @@ export async function Blog() {
                   href={post.href}
                   className="flex items-center gap-1 font-bold text-body whitespace-nowrap hover:text-brand transition-colors"
                 >
-                  <span aria-hidden>→</span>
+                  <ArrowRightIcon />
                   <span>Zum Beitrag</span>
                 </Link>
               </div>