## Problem
Sentry:
[PHP-LARAVEL-1Z](https://whisper-money.sentry.io/issues/PHP-LARAVEL-1Z)
— 5 events.
`ResendTransport::doSend` throws `TransportException: Invalid \`to\`
field` when a notifiable's email fails Resend's RFC validation
(malformed address, whitespace, etc.). The queued notification job dies
and we get paged.
Stacktrace path: `SendQueuedNotifications → NotificationSender →
MailChannel → ResendTransport`. Mail channel calls
`routeNotificationForMail()` on the notifiable to resolve the address;
both `User` and `UserLead` were returning the raw `email` column without
format checks.
## Fix
Validate the address in `routeNotificationForMail()` on both models:
- trim whitespace
- run `filter_var(..., FILTER_VALIDATE_EMAIL)`
- return `null` (skips the channel) when invalid
- log a warning with model id + notification class for triage
Other channels (database, etc.) keep working.
## Test
New `tests/Feature/RouteNotificationForMailTest.php` covers valid,
malformed, whitespace, and trimmed cases on both `User` and `UserLead`.
```
php artisan test --filter='RouteNotificationForMailTest|UserLeadTest|VerificationNotificationTest|UserLeadInvitationTest|SendUserLeadInvitations'
Tests: 48 passed
```
Fixes PHP-LARAVEL-1Z
d140b4fd4c