Add option to ignore SSL/TLS certificate errors for email (Issue #53)

This feature allows users with non-standard SMTP setups (shared hosting,
self-signed certificates) to bypass certificate validation when needed.

Changes:
- Add database migration for tls_reject_unauthorized column
- Update emailProcessor.js to pass TLS option to nodemailer
- Update adminEmail.js routes to handle the new field
- Add checkbox UI with security warning in EmailConfigPage
- Add English and German translations

frontend/src/services/email.service.ts

@@ -8,6 +8,7 @@ export interface EmailConfig {
   smtp_pass: string;
   from_email: string;
   from_name: string;
+  tls_reject_unauthorized: boolean;
 }
 
 export interface EmailTemplate {