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.

server/config/database.js

@@ -1,4 +1,4 @@
-import bcrypt from 'bcryptjs';
+import bcrypt from 'bcryptjs';
 import path from 'path';
 import { fileURLToPath } from 'url';
 import { log } from './logger.js';
@@ -106,7 +106,7 @@ class PostgresAdapter {
 // ── Public API ──────────────────────────────────────────────────────────────
 export function getDb() {
   if (!db) {
-    throw new Error('Database not initialised – call initDatabase() first');
+    throw new Error('Database not initialised - call initDatabase() first');
   }
   return db;
 }