Add pages, update App layout and i18n

Introduce LandingPage, LoginPage and ImprintPage components and replace the previous inline placeholders in App.jsx. Update App layout and header (branding, language toggle, dark mode toggle, route wiring) and use new i18n keys (IMPRINT and LOGIN) in en/de locales. Add client-side validation and UI for the login form. Remove unused assets/icons (public/icons.svg, src/assets/hero.png, vite.svg, vue.svg). Small logging/message tweaks and various Tailwind styling refinements.

src/pages/ImprintPage.jsx

@@ -0,0 +1,28 @@
+import {useTranslation} from 'react-i18next';
+
+export default function ImprintPage() {
+    const {t} = useTranslation();
+
+    return (
+        <div className="grow flex justify-center p-4 md:p-8">
+            <div className="w-full max-w-3xl bg-white dark:bg-slate-900 border border-slate-200 dark:border-slate-800 rounded-2xl p-8 shadow-sm">
+                <h1 className="text-3xl font-black text-slate-900 dark:text-white mb-6">
+                    {t('IMPRINT.TITLE')}
+                </h1>
+                <div className="text-slate-600 dark:text-slate-400 space-y-4">
+                    <p>{t('IMPRINT.LEGAL')}</p>
+                    <p>
+                        <strong>Andreas Dahm</strong><br/>
+                        Bgm.-Germeier-Str. 2<br/>
+                        85586 Poing<br/>
+                        Deutschland
+                    </p>
+                    <h2 className="text-xl font-bold text-slate-900 dark:text-white mt-8">
+                        {t('IMPRINT.CONTACT')}
+                    </h2>
+                    <p>Email: andreas.dahm@gmail.com</p>
+                </div>
+            </div>
+        </div>
+    );
+}