fix(notifications): skip mail dispatch when recipient email is invalid (#387)

## 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

app/Models/User.php

@@ -17,6 +17,7 @@ use Illuminate\Foundation\Auth\User as Authenticatable;
 use Illuminate\Notifications\Notifiable;
 use Illuminate\Notifications\Notification;
 use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Log;
 use Laravel\Cashier\Billable;
 use Laravel\Fortify\TwoFactorAuthenticatable;
 use Laravel\Pennant\Concerns\HasFeatures;
@@ -216,7 +217,18 @@ class User extends Authenticatable implements HasLocalePreference, MustVerifyEma
             return null;
         }
 
-        return $this->email;
+        $email = trim((string) $this->email);
+
+        if ($email === '' || filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
+            Log::warning('Skipping mail notification: invalid recipient email', [
+                'user_id' => $this->getKey(),
+                'notification' => $notification ? $notification::class : null,
+            ]);
+
+            return null;
+        }
+
+        return $email;
     }
 
     public function sendEmailVerificationNotification(): void

app/Models/UserLead.php

@@ -13,6 +13,8 @@ use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Notifications\Notifiable;
+use Illuminate\Notifications\Notification;
+use Illuminate\Support\Facades\Log;
 use Illuminate\Support\Str;
 
 /**
@@ -124,6 +126,22 @@ class UserLead extends Model implements HasLocalePreference, MustVerifyEmail
         return $this->locale ?? 'en';
     }
 
+    public function routeNotificationForMail(?Notification $notification = null): ?string
+    {
+        $email = trim((string) $this->email);
+
+        if ($email === '' || filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
+            Log::warning('Skipping mail notification: invalid recipient email', [
+                'user_lead_id' => $this->getKey(),
+                'notification' => $notification ? $notification::class : null,
+            ]);
+
+            return null;
+        }
+
+        return $email;
+    }
+
     public function getEmailForVerification(): string
     {
         return $this->email;

tests/Feature/RouteNotificationForMailTest.php

@@ -0,0 +1,52 @@
+<?php
+
+use App\Models\User;
+use App\Models\UserLead;
+use App\Notifications\VerifyEmailNotification;
+use App\Notifications\VerifyUserLeadEmailNotification;
+
+test('user returns email for mail routing when valid', function () {
+    $user = User::factory()->create(['email' => 'valid@example.com']);
+
+    expect($user->routeNotificationForMail(new VerifyEmailNotification))
+        ->toBe('valid@example.com');
+});
+
+test('user skips mail routing when email is malformed', function () {
+    $user = User::factory()->create();
+    $user->forceFill(['email' => 'not-an-email'])->saveQuietly();
+
+    expect($user->routeNotificationForMail(new VerifyEmailNotification))
+        ->toBeNull();
+});
+
+test('user skips mail routing when email has surrounding whitespace it cannot parse', function () {
+    $user = User::factory()->create();
+    $user->forceFill(['email' => ' '])->saveQuietly();
+
+    expect($user->routeNotificationForMail(new VerifyEmailNotification))
+        ->toBeNull();
+});
+
+test('user trims valid email before routing', function () {
+    $user = User::factory()->create();
+    $user->forceFill(['email' => "  spaced@example.com\n"])->saveQuietly();
+
+    expect($user->routeNotificationForMail(new VerifyEmailNotification))
+        ->toBe('spaced@example.com');
+});
+
+test('user lead returns email for mail routing when valid', function () {
+    $lead = UserLead::factory()->create(['email' => 'lead@example.com']);
+
+    expect($lead->routeNotificationForMail(new VerifyUserLeadEmailNotification('https://example.com')))
+        ->toBe('lead@example.com');
+});
+
+test('user lead skips mail routing when email is malformed', function () {
+    $lead = UserLead::factory()->create();
+    $lead->forceFill(['email' => 'broken@@example'])->saveQuietly();
+
+    expect($lead->routeNotificationForMail(new VerifyUserLeadEmailNotification('https://example.com')))
+        ->toBeNull();
+});