feat(website): localize whitelabel partner cards (da/en)

Partner demo cards in section 06 were hardcoded Danish strings, so they
stayed Danish in EN mode. Move name + subtitle into COPY.whitelabel.partners
for both languages and render them via a mapped computed; per-card accent and
the placeholder style remain presentational config in the component.

Also harden PartnerCard's avatar-initial against an empty name to satisfy
noUncheckedIndexedAccess.

apps/website/utils/landingCopy.ts

@@ -81,6 +81,11 @@ export const COPY = {
         'Co-marketing og kundeleads via partnernetværk',
       ],
       cta: 'Se partnerprogrammet',
+      partners: [
+        { name: 'moltke it', subtitle: 'aalborg · 24 brugere' },
+        { name: 'kraft & partners', subtitle: 'københavn · 112 brugere' },
+        { name: 'dit firma her', subtitle: '—' },
+      ],
     },
     stack: {
       label: '07 — under motorhjelmen',
@@ -210,6 +215,11 @@ export const COPY = {
         'Co-marketing and leads via partner network',
       ],
       cta: 'See the partner program',
+      partners: [
+        { name: 'moltke it', subtitle: 'aalborg · 24 users' },
+        { name: 'kraft & partners', subtitle: 'copenhagen · 112 users' },
+        { name: 'your company here', subtitle: '—' },
+      ],
     },
     stack: {
       label: '07 — under the hood',