feat(notifications): deduplicate repeated email alerts

Add notification-level deduplication keys and TTLs for deployment, backup,
server, container, scheduled task, SSL, token, and transactional emails.
Apply deduplication in email channels before sending rendered messages.

app/Notifications/Channels/EmailChannel.php

@@ -4,13 +4,20 @@ namespace App\Notifications\Channels;
 
 use App\Exceptions\NonReportableException;
 use App\Models\Team;
+use App\Services\NotificationDeduplicator;
 use Exception;
 use Illuminate\Notifications\Notification;
 use Resend;
+use Resend\Exceptions\ErrorException;
+use Resend\Exceptions\TransporterException;
+use Symfony\Component\Mailer\Mailer;
+use Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport;
+use Symfony\Component\Mime\Address;
+use Symfony\Component\Mime\Email;
 
 class EmailChannel
 {
-    public function __construct() {}
+    public function __construct(private NotificationDeduplicator $deduplicator) {}
 
     public function send(SendsEmail $notifiable, Notification $notification): void
     {
@@ -67,6 +74,11 @@ class EmailChannel
             }
 
             $mailMessage = $notification->toMail($notifiable);
+            $renderedMail = (string) $mailMessage->render();
+
+            if (! $this->deduplicator->shouldSend($notifiable, $notification, self::class, $recipients, $mailMessage->subject, $renderedMail)) {
+                return;
+            }
 
             if ($isResendEnabled) {
                 $resend = Resend::client($settings->resend_api_key);
@@ -75,17 +87,17 @@ class EmailChannel
                     'from' => $from,
                     'to' => $recipients,
                     'subject' => $mailMessage->subject,
-                    'html' => (string) $mailMessage->render(),
+                    'html' => $renderedMail,
                 ]);
             } elseif ($isSmtpEnabled) {
-                $encryption = match (strtolower($settings->smtp_encryption)) {
+                $encryption = match (strtolower($settings->smtp_encryption ?? '')) {
                     'starttls' => null,
                     'tls' => 'tls',
                     'none' => null,
                     default => null,
                 };
 
-                $transport = new \Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport(
+                $transport = new EsmtpTransport(
                     $settings->smtp_host,
                     $settings->smtp_port,
                     $encryption
@@ -93,20 +105,20 @@ class EmailChannel
                 $transport->setUsername($settings->smtp_username ?? '');
                 $transport->setPassword($settings->smtp_password ?? '');
 
-                $mailer = new \Symfony\Component\Mailer\Mailer($transport);
+                $mailer = new Mailer($transport);
 
                 $fromEmail = $settings->smtp_from_address ?? 'noreply@localhost';
                 $fromName = $settings->smtp_from_name ?? 'System';
-                $from = new \Symfony\Component\Mime\Address($fromEmail, $fromName);
-                $email = (new \Symfony\Component\Mime\Email)
+                $from = new Address($fromEmail, $fromName);
+                $email = (new Email)
                     ->from($from)
                     ->to(...$recipients)
                     ->subject($mailMessage->subject)
-                    ->html((string) $mailMessage->render());
+                    ->html($renderedMail);
 
                 $mailer->send($email);
             }
-        } catch (\Resend\Exceptions\ErrorException $e) {
+        } catch (ErrorException $e) {
             // Map HTTP status codes to user-friendly messages
             $userMessage = match ($e->getErrorCode()) {
                 403 => 'Invalid Resend API key. Please verify your API key in the Resend dashboard and update it in settings.',
@@ -131,13 +143,13 @@ class EmailChannel
 
             // Don't report expected errors (invalid keys, validation) to Sentry
             if (in_array($e->getErrorCode(), [403, 401, 400])) {
-                throw NonReportableException::fromException(new \Exception($userMessage, $e->getCode(), $e));
+                throw NonReportableException::fromException(new Exception($userMessage, $e->getCode(), $e));
             }
 
-            throw new \Exception($userMessage, $e->getCode(), $e);
-        } catch (\Resend\Exceptions\TransporterException $e) {
+            throw new Exception($userMessage, $e->getCode(), $e);
+        } catch (TransporterException $e) {
             send_internal_notification("Resend Transport Error: {$e->getMessage()}");
-            throw new \Exception('Unable to connect to Resend API. Please check your internet connection and try again.');
+            throw new Exception('Unable to connect to Resend API. Please check your internet connection and try again.');
         } catch (\Throwable $e) {
             // Check if this is a Resend domain verification error on cloud instances
             if (isCloud() && str_contains($e->getMessage(), 'domain is not verified')) {

app/Notifications/Channels/TransactionalEmailChannel.php

@@ -3,6 +3,7 @@
 namespace App\Notifications\Channels;
 
 use App\Models\User;
+use App\Services\NotificationDeduplicator;
 use Exception;
 use Illuminate\Mail\Message;
 use Illuminate\Notifications\Notification;
@@ -10,6 +11,8 @@ use Illuminate\Support\Facades\Mail;
 
 class TransactionalEmailChannel
 {
+    public function __construct(private NotificationDeduplicator $deduplicator) {}
+
     public function send(User $notifiable, Notification $notification): void
     {
         $settings = instanceSettings();
@@ -27,13 +30,19 @@ class TransactionalEmailChannel
         }
         $this->bootConfigs();
         $mailMessage = $notification->toMail($notifiable);
+        $renderedMail = (string) $mailMessage->render();
+
+        if (! $this->deduplicator->shouldSend($notifiable, $notification, self::class, [$email], $mailMessage->subject, $renderedMail)) {
+            return;
+        }
+
         Mail::send(
             [],
             [],
             fn (Message $message) => $message
                 ->to($email)
                 ->subject($mailMessage->subject)
-                ->html((string) $mailMessage->render())
+                ->html($renderedMail)
         );
     }