fix: respect SMTP encryption setting for email notifications

The EsmtpTransport constructor expects bool|null for the tls parameter:
- null: auto-detect (try STARTTLS if supported)
- true: force implicit TLS (port 465)
- false: no encryption

Previously 'none' mapped to null which still attempted STARTTLS,
and 'tls' mapped to the string 'tls' instead of boolean true.

Fixes #6442

app/Notifications/Channels/EmailChannel.php

@@ -80,8 +80,8 @@ class EmailChannel
             } elseif ($isSmtpEnabled) {
                 $encryption = match (strtolower($settings->smtp_encryption)) {
                     'starttls' => null,
-                    'tls' => 'tls',
-                    'none' => null,
+                    'tls' => true,
+                    'none' => false,
                     default => null,
                 };