Add password reset, order confirmation email with editable templates, and fix missing account entry points

Password reset uses Payload's built-in forgot/reset-password flow,
customized to link to this app instead of the Payload admin. Order
confirmation email and the password-reset email's wording both come from
a new Payload email-templates collection, editable without a deploy and
previewable via Live Preview at /email-preview/[type] (same mechanism as
Posts/LegalPages/Testimonials, sample data instead of a real document).

Also: order numbers get a random suffix (prevents guessing, motivated by
a considered-and-deferred guest order-lookup feature); the discount code
field only shows in the cart when a code is actually active (codes now
apply via a ?code= link instead of manual entry); and three navigation
gaps found while testing — no reachable login link with an empty cart, no
logout link anywhere, no way back from profile to order history.

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

app/checkout/components/CheckoutContent.tsx

@@ -311,16 +311,22 @@ export function CheckoutContent({
             {/* Only needed for the inline-registration path — an existing
                 session already has an account, no password to collect. */}
             {!customerEmail && (
-              <FormField
-                label="Passwort (für dein neues Konto)"
-                name="password"
-                type="password"
-                placeholder="Mind. 8 Zeichen"
-                autoComplete="new-password"
-                required
-                minLength={8}
-                wrapperClassName="w-full sm:w-[calc(50%-0.5rem)] sm:flex-none min-w-0"
-              />
+              <div className="flex flex-col gap-2 w-full sm:w-[calc(50%-0.5rem)] sm:flex-none min-w-0">
+                <FormField
+                  label="Passwort (für dein neues Konto)"
+                  name="password"
+                  type="password"
+                  placeholder="Mind. 8 Zeichen"
+                  autoComplete="new-password"
+                  required
+                  minLength={8}
+                  wrapperClassName="w-full"
+                />
+                <p className="text-label text-text-muted">
+                  Mit dem Kauf legen wir automatisch ein Konto für dich an — damit du deine Bestellungen später
+                  einsehen und bei Bedarf stornieren oder zurücksenden kannst.
+                </p>
+              </div>
             )}
             {/* Segmented control, same sm:w-[calc(50%-0.5rem)] half-row
                 width as the field(s) below it — Lieferadresse keeps