feat: 重要通知模块、Server 酱独立配置与额度提醒

- 新增重要通知统一模块（邮件 + Server 酱）作为后台任务通知出口
- 拆出独立的 Server 酱 配置页（SendKey + Markdown 模板，支持 {title}/{body} 变量替换），通过仪表盘内置工具入口进入
- 新增提供商额度提醒后台 worker：余额低于阈值时通过重要通知推送，提供商配置页加入额度提醒开关与阈值
- 重要通知页加入配置可用性守卫：未配置任一通道时禁用总开关，未配置邮件/SendKey 时禁用对应通道开关
- 测试通知端点支持 channel 过滤（all/email/server_chan），并绕过总开关与通道开关，便于配置阶段先验证通道
- 修复：测试通知路由未在 buffered-body 白名单导致 channel 参数丢失、测试时邮件分支被误触发
- 修复：sub2api 验证响应中 username 为 null 时正确回退到 email，避免误报"验证响应缺少: 用户信息"

Co-Authored-By: Claude Opus 4.7 <[email protected]>

crates/aether-admin/src/provider/ops/verify.rs

@@ -797,22 +797,13 @@ pub fn admin_provider_ops_sub2api_verify_payload(
         }
     }
 
+    let username_or_email = admin_provider_ops_sub2api_non_empty_string(user_data, "username")
+        .or_else(|| admin_provider_ops_sub2api_non_empty_string(user_data, "email"));
     admin_provider_ops_verify_success(
         admin_provider_ops_verify_user_payload(
-            user_data
-                .get("username")
-                .or_else(|| user_data.get("email"))
-                .and_then(Value::as_str)
-                .map(ToOwned::to_owned),
-            user_data
-                .get("username")
-                .or_else(|| user_data.get("email"))
-                .and_then(Value::as_str)
-                .map(ToOwned::to_owned),
-            user_data
-                .get("email")
-                .and_then(Value::as_str)
-                .map(ToOwned::to_owned),
+            username_or_email.clone(),
+            username_or_email,
+            admin_provider_ops_sub2api_non_empty_string(user_data, "email"),
             Some(balance + points),
             Some(extra),
         ),
@@ -820,6 +811,17 @@ pub fn admin_provider_ops_sub2api_verify_payload(
     )
 }
 
+fn admin_provider_ops_sub2api_non_empty_string(
+    map: &Map<String, Value>,
+    key: &str,
+) -> Option<String> {
+    map.get(key)
+        .and_then(Value::as_str)
+        .map(str::trim)
+        .filter(|value| !value.is_empty())
+        .map(ToOwned::to_owned)
+}
+
 #[cfg(test)]
 mod tests {
     use super::{
@@ -913,6 +915,28 @@ mod tests {
         );
     }
 
+    #[test]
+    fn sub2api_verify_payload_falls_back_to_email_when_username_is_null() {
+        let payload = admin_provider_ops_sub2api_verify_payload(
+            StatusCode::OK,
+            &json!({
+                "code": 0,
+                "data": {
+                    "username": null,
+                    "email": "[email protected]",
+                    "balance": 2.0,
+                    "points": 0.0
+                }
+            }),
+            None,
+        );
+
+        assert_eq!(payload["success"], json!(true));
+        assert_eq!(payload["data"]["username"], json!("[email protected]"));
+        assert_eq!(payload["data"]["display_name"], json!("[email protected]"));
+        assert_eq!(payload["data"]["email"], json!("[email protected]"));
+    }
+
     #[test]
     fn anyrouter_verify_payload_uses_cookie_auth_messages_and_usage_fields() {
         let payload = admin_provider_ops_anyrouter_verify_payload(