feat: add discreet Ko-fi support badge in app footer

Let users support project development and running costs via ko-fi.com/kapteinsdaagbok, with i18n tooltips and Plausible tracking.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/components/AppFooter.tsx

@@ -1,8 +1,13 @@
+import { Coffee } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { PlausibleEvents, trackPlausibleEvent } from '../services/analytics.js'
 
 const APP_VERSION = typeof __APP_VERSION__ !== 'undefined' ? __APP_VERSION__ : 'dev'
+const KOFI_URL = 'https://ko-fi.com/kapteinsdaagbok'
 
 export default function AppFooter() {
+  const { t } = useTranslation()
+
   return (
     <footer className="app-version-footer">
       <span className="app-version-footer__version">v{APP_VERSION}</span>
@@ -18,6 +23,21 @@ export default function AppFooter() {
           Markus F.J. Busche
         </a>
       </span>
+      <span className="app-version-footer__sep" aria-hidden="true">
+        ·
+      </span>
+      <a
+        className="kofi-footer-badge"
+        href={KOFI_URL}
+        target="_blank"
+        rel="noopener noreferrer"
+        title={t('footer.kofi_title')}
+        aria-label={t('footer.kofi_title')}
+        onClick={() => trackPlausibleEvent(PlausibleEvents.KOFI_LINK_CLICKED)}
+      >
+        <Coffee size={12} aria-hidden="true" />
+        <span>{t('footer.kofi_label')}</span>
+      </a>
     </footer>
   )
 }