Refactor code and improve internationalization support

- Updated import statements to remove invisible characters.
- Standardized comments to use a consistent hyphen format.
- Adjusted username validation error messages for consistency.
- Enhanced email sending functions to include language support.
- Added email internationalization configuration for dynamic translations.
- Updated calendar and federation routes to include language in user queries.
- Improved user feedback messages in German and English for clarity.

src/pages/FederationInbox.jsx

@@ -1,4 +1,4 @@
-import { useState, useEffect } from 'react';
+import { useState, useEffect } from 'react';
 import { Globe, Mail, Check, X, ExternalLink, Loader2, Inbox, Calendar, Trash2 } from 'lucide-react';
 import api from '../services/api';
 import { useLanguage } from '../contexts/LanguageContext';
@@ -210,7 +210,7 @@ export default function FederationInbox() {
                                             {t('federation.from')}: <span className="font-medium text-th-text">{inv.from_user}</span>
                                         </p>
                                         <p className="text-sm text-th-text-s mt-1">
-                                            {new Date(inv.start_time).toLocaleString()} – {new Date(inv.end_time).toLocaleString()}
+                                            {new Date(inv.start_time).toLocaleString()} - {new Date(inv.end_time).toLocaleString()}
                                         </p>
                                         {inv.description && (
                                             <p className="text-sm text-th-text-s mt-1 italic">"{inv.description}"</p>
@@ -249,7 +249,7 @@ export default function FederationInbox() {
                                             {t('federation.from')}: <span className="font-medium text-th-text">{inv.from_name}</span>
                                         </p>
                                         <p className="text-sm text-th-text-s mt-1">
-                                            {new Date(inv.start_time).toLocaleString()} – {new Date(inv.end_time).toLocaleString()}
+                                            {new Date(inv.start_time).toLocaleString()} - {new Date(inv.end_time).toLocaleString()}
                                         </p>
                                         {inv.description && (
                                             <p className="text-sm text-th-text-s mt-1 italic">"{inv.description}"</p>