feat(provider): allow optional username and password in email notifier

ui/src/components/access/forms/AccessConfigFieldsProviderEmail.tsx

@@ -130,8 +130,8 @@ const getSchema = ({ i18n = getI18n() }: { i18n: ReturnType<typeof getI18n> }) =
     smtpHost: z.string().refine((v) => isHostname(v), t("common.errmsg.host_invalid")),
     smtpPort: z.coerce.number().refine((v) => isPortNumber(v), t("common.errmsg.port_invalid")),
     smtpTls: z.boolean().nullish(),
-    username: z.string().nonempty(),
-    password: z.string().nonempty(),
+    username: z.string().nullish(),
+    password: z.string().nullish(),
     senderAddress: z.email(),
     senderName: z.string().nullish(),
     receiverAddress: z.email().or(z.literal("")).nullish(),

ui/src/i18n/resources/en/nls.access.json

@@ -529,12 +529,12 @@
       }
     },
     "email_username": {
-      "label": "Username",
-      "placeholder": "please enter username"
+      "label": "Username (Optional)",
+      "placeholder": "please enter SMTP username"
     },
     "email_password": {
-      "label": "Password",
-      "placeholder": "please enter password"
+      "label": "Password (Optional)",
+      "placeholder": "please enter SMTP password"
     },
     "email_sender_address": {
       "label": "Sender email address",

ui/src/i18n/resources/zh/nls.access.json

@@ -527,12 +527,12 @@
       }
     },
     "email_username": {
-      "label": "用户名",
-      "placeholder": "请输入用户名"
+      "label": "用户名（可选）",
+      "placeholder": "请输入 SMTP 用户名"
     },
     "email_password": {
-      "label": "密码",
-      "placeholder": "请输入密码"
+      "label": "密码（可选）",
+      "placeholder": "请输入 SMTP 密码"
     },
     "email_sender_address": {
       "label": "发件人邮箱",