feat: add config for mail server name (#13632)

fix #13627

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Added configurable display names for primary and fallback SMTP
servers, improving email sender identification.
* Defaults to “AFFiNE Server,” with support for MAILER_SERVERNAME
environment variable for the primary SMTP.
* Exposed in admin settings for easy setup alongside existing SMTP
options.
* Names are now passed through to mail transport options for consistent
use across emails.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/core/mail/config.ts

@@ -6,6 +6,7 @@ declare global {
   interface AppConfigSchema {
     mailer: {
       SMTP: {
+        name: string;
         host: string;
         port: number;
         username: string;
@@ -16,6 +17,7 @@ declare global {
 
       fallbackDomains: ConfigItem<string[]>;
       fallbackSMTP: {
+        name: string;
         host: string;
         port: number;
         username: string;
@@ -28,6 +30,11 @@ declare global {
 }
 
 defineModuleConfig('mailer', {
+  'SMTP.name': {
+    desc: 'Name of the email server (e.g. your domain name)',
+    default: 'AFFiNE Server',
+    env: 'MAILER_SERVERNAME',
+  },
   'SMTP.host': {
     desc: 'Host of the email server (e.g. smtp.gmail.com)',
     default: '',
@@ -64,6 +71,10 @@ defineModuleConfig('mailer', {
     default: [],
     shape: z.array(z.string()),
   },
+  'fallbackSMTP.name': {
+    desc: 'Name of the fallback email server (e.g. your domain name)',
+    default: 'AFFiNE Server',
+  },
   'fallbackSMTP.host': {
     desc: 'Host of the email server (e.g. smtp.gmail.com)',
     default: '',

packages/backend/server/src/core/mail/sender.ts

@@ -20,6 +20,7 @@ function configToSMTPOptions(
   config: AppConfig['mailer']['SMTP']
 ): SMTPTransport.Options {
   return {
+    name: config.name,
     host: config.host,
     port: config.port,
     tls: {