Fix navbar/discount/invoice bugs from manual QA, add VAT breakdown, shipping-address override, checkout persistence, redesigned mobile menu

Bug fixes:
- Navbar login/logout state now updates immediately (custom ep-auth-changed
  event) instead of requiring a hard reload
- Status-change email links were broken by an un-encoded "#" in the order
  number; fixed for all 4 status emails
- Cart discount code: manual input field restored (was removed entirely)
- Quote-label underline now scales with the label's actual text width
- Number Ranges admin list now shows the invoice prefix/counter columns

Pricing & VAT:
- Prices show the real per-product VAT rate ("inkl. X% MwSt.") instead of
  a generic disclosure
- Cart/checkout/confirmation totals show the actual € amount of VAT
  included, broken down per rate when a cart spans more than one
  (new lib/taxBreakdown.ts, shared with the invoice PDF's own math)
- Account order pages gained product thumbnails and the same VAT breakdown

Low-stock warning: a "Nur noch wenige verfügbar" badge/hint across the
shop grid, spotlight, and add-to-cart variant pickers, driven by the
existing lowStockThreshold field (still never exposes raw stock counts).

Invoice PDFs: product thumbnails on every line item, a plain "Netto"
label (rate was redundant, already stated on the MwSt. line below), no
more duplicate USt-IdNr. in the header, and — for a Stornorechnung
specifically — an explicit "Versand" line that was previously only
folded silently into the tax totals.

Checkout:
- Optional deviating shipping address (separate from the billing address
  used for the invoice), with its own toggle + address form
- Full checkout draft persistence (name/address/shipping/payment
  selections) survives navigating away and back, via localStorage
- Invoice PDF shows a third "Lieferadresse" block when the shipping
  address differs from billing

Mobile navigation: fullscreen panel with a circular reveal animation from
the hamburger's corner, replacing the old in-flow accordion drawer; no
login CTA inside it (redundant with the always-visible header icon).

Admin-facing (Payload backend, mirrored where the frontend has a ported
copy of the same renderer): dashboard rebuilt as individual cards, split
into 3 task queues (received/processing/returns) instead of 2, revenue
and order counts now exclude cancelled/returned orders immediately, and
the low-stock alert links to the specific affected product(s) instead of
the unfiltered list. A new immediate email notifies the shop owner the
moment an order comes in, instead of only via the daily digest.

Testimonials admin list now groups by page instead of interleaving all
three grids' entries. ~45 English admin field descriptions translated to
German for consistency.

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

app/todo-cards/components/Pricing.tsx

@@ -1,8 +1,9 @@
 import Image from "next/image";
 import { AddToCartButton } from "../../components/AddToCartButton";
 import { Reveal } from "../../components/Reveal";
-import { getProductBySlug, getShippingSettings } from "../../lib/payload";
+import { getProductBySlug, getShippingSettings, getDefaultTaxRatePercent } from "../../lib/payload";
 import { formatPrice, discountPercent } from "../../lib/format";
+import { effectiveTaxRate } from "../../lib/cartTotals";
 
 const bullets = [
   "50 ToDo-Karten",
@@ -17,9 +18,14 @@ const bullets = [
 // reasoning; the bullet list stays hand-written since it's spec detail,
 // not something the Products collection models.
 export async function Pricing() {
-  const [product, shipping] = await Promise.all([getProductBySlug("todo-karten"), getShippingSettings()]);
+  const [product, shipping, defaultTaxRate] = await Promise.all([
+    getProductBySlug("todo-karten"),
+    getShippingSettings(),
+    getDefaultTaxRatePercent(),
+  ]);
   if (!product) return null;
   const discount = discountPercent(product.price, product.compareAtPrice);
+  const taxRate = effectiveTaxRate(product, defaultTaxRate);
 
   return (
     <section className="w-full bg-bg-base px-[var(--layout-padding-x)] py-8">
@@ -66,7 +72,7 @@ export async function Pricing() {
                 <p className="text-body text-text-muted line-through">{formatPrice(product.compareAtPrice!)}</p>
               )}
               <p className="font-bold text-h3 text-text-primary">{formatPrice(product.price)}</p>
-              <p className="text-label text-text-muted">inkl. MwSt. zzgl. Versand</p>
+              <p className="text-label text-text-muted">inkl. {taxRate}% MwSt. zzgl. Versand</p>
             </div>
             <p className="text-label text-text-muted">
               Lieferzeit: {shipping.totalDays.min}–{shipping.totalDays.max} Werktage innerhalb Deutschlands
@@ -80,6 +86,7 @@ export async function Pricing() {
             label="In den Warenkorb"
             className="w-full inline-flex items-center justify-center px-6 py-[0.8125rem] rounded-sm bg-brand hover:bg-brand-hover active:scale-[0.97] transition-all font-bold text-body text-text-primary text-center focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-brand focus-visible:ring-offset-2 focus-visible:ring-offset-bg-muted"
             outOfStock={product.outOfStock}
+            lowStock={product.lowStock}
             variants={product.variants}
           />
         </div>

app/todo-cards/components/TodoKartenHero.tsx

@@ -2,8 +2,9 @@ import Link from "next/link";
 import Image from "next/image";
 import { AddToCartButton } from "../../components/AddToCartButton";
 import { Reveal } from "../../components/Reveal";
-import { getProductBySlug, getShippingSettings } from "../../lib/payload";
+import { getProductBySlug, getShippingSettings, getDefaultTaxRatePercent } from "../../lib/payload";
 import { formatPrice, discountPercent } from "../../lib/format";
+import { effectiveTaxRate } from "../../lib/cartTotals";
 
 const checklist = [
   "Klarer Fokus auf das, was wirklich zählt",
@@ -18,8 +19,13 @@ const checklist = [
 // §1 Abs.1 Nr.8 EGBGB's delivery-date disclosure needs to sit next to every
 // buy button, not just one of them.
 export async function TodoKartenHero() {
-  const [product, shipping] = await Promise.all([getProductBySlug("todo-karten"), getShippingSettings()]);
+  const [product, shipping, defaultTaxRate] = await Promise.all([
+    getProductBySlug("todo-karten"),
+    getShippingSettings(),
+    getDefaultTaxRatePercent(),
+  ]);
   const discount = product ? discountPercent(product.price, product.compareAtPrice) : null;
+  const taxRate = product ? effectiveTaxRate(product, defaultTaxRate) : null;
 
   return (
     <section className="bg-bg-base w-full overflow-hidden">
@@ -99,7 +105,7 @@ export async function TodoKartenHero() {
                     <p className="text-body text-text-muted line-through">{formatPrice(product.compareAtPrice!)}</p>
                   )}
                   <p className="font-bold text-h3 text-text-primary">{formatPrice(product.price)}</p>
-                  <p className="text-label text-text-muted">inkl. MwSt.</p>
+                  <p className="text-label text-text-muted">inkl. {taxRate}% MwSt.</p>
                 </div>
               )}
               <p className="text-label text-text-muted">
@@ -108,7 +114,7 @@ export async function TodoKartenHero() {
             </div>
 
             {product && (
-              <AddToCartButton label="ToDo-Karten bestellen" outOfStock={product.outOfStock} variants={product.variants} />
+              <AddToCartButton label="ToDo-Karten bestellen" outOfStock={product.outOfStock} lowStock={product.lowStock} variants={product.variants} />
             )}
           </div>
         </Reveal>