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

backend/migrations/core/047_add_tls_reject_unauthorized.js

@@ -0,0 +1,18 @@
+const { addColumnIfNotExists } = require('../helpers');
+
+exports.up = async function up(knex) {
+  // Add tls_reject_unauthorized column to email_configs table
+  // Default is true (validate certificates), false means ignore SSL/TLS certificate errors
+  await addColumnIfNotExists(knex, 'email_configs', 'tls_reject_unauthorized', (table) => {
+    table.boolean('tls_reject_unauthorized').defaultTo(true);
+  });
+};
+
+exports.down = async function down(knex) {
+  const hasColumn = await knex.schema.hasColumn('email_configs', 'tls_reject_unauthorized');
+  if (hasColumn) {
+    await knex.schema.alterTable('email_configs', (table) => {
+      table.dropColumn('tls_reject_unauthorized');
+    });
+  }
+};