feat: implement comprehensive i18n system with German and English support

- Created type-safe i18n system with TranslationKeys interface
- Added German (de) and English (en) translations with 160+ keys
- Implemented I18nContext provider and useI18n hook
- Added LanguageSwitcher component for language selection
- Refactored all major components to use translations:
  * Home page, StatsDashboard, DramOfTheDay
  * BottleGrid, EditBottleForm, CameraCapture
  * BuddyList, SessionList, TastingNoteForm
  * StatusSwitcher and bottle management features
- Implemented locale-aware currency formatting (EUR)
- Implemented locale-aware date formatting
- Added localStorage persistence for language preference
- Added automatic browser language detection
- Organized translations into 8 main categories
- System is extensible for additional languages

src/components/LanguageSwitcher.tsx

@@ -0,0 +1,35 @@
+'use client';
+
+import React from 'react';
+import { useI18n } from '@/i18n/I18nContext';
+
+const LanguageSwitcher = () => {
+    const { locale, setLocale } = useI18n();
+
+    return (
+        <div className="flex items-center gap-2">
+            <button
+                onClick={() => setLocale('de')}
+                className={`p-1.5 rounded-lg transition-all ${locale === 'de'
+                        ? 'bg-amber-100 dark:bg-amber-900/30 scale-110 shadow-sm'
+                        : 'opacity-50 hover:opacity-100 grayscale hover:grayscale-0'
+                    }`}
+                title="Deutsch"
+            >
+                <span className="text-lg">🇩🇪</span>
+            </button>
+            <button
+                onClick={() => setLocale('en')}
+                className={`p-1.5 rounded-lg transition-all ${locale === 'en'
+                        ? 'bg-amber-100 dark:bg-amber-900/30 scale-110 shadow-sm'
+                        : 'opacity-50 hover:opacity-100 grayscale hover:grayscale-0'
+                    }`}
+                title="English"
+            >
+                <span className="text-lg">🇬🇧</span>
+            </button>
+        </div>
+    );
+};
+
+export default LanguageSwitcher;