feat(auth): implement password reset functionality

- Added new endpoints for requesting and resetting passwords in the authController.
- Updated User model to include resetToken and resetTokenExpires fields for managing password reset requests.
- Enhanced emailService to send password reset emails with secure links.
- Updated frontend routes and views to support password reset flow, including new ForgotPassword and ResetPassword components.
- Improved internationalization files with new translation keys for password reset messages across multiple languages.

backend/migrations/20260130_add_password_reset_fields.sql

@@ -0,0 +1,8 @@
+-- Felder für "Passwort vergessen"-Funktion
+ALTER TABLE user
+ADD COLUMN reset_token VARCHAR(255) NULL DEFAULT NULL
+COMMENT 'Token für Passwort-Reset';
+
+ALTER TABLE user
+ADD COLUMN reset_token_expires DATETIME NULL DEFAULT NULL
+COMMENT 'Ablaufzeitpunkt des Reset-Tokens';