fix(admin): 修复系统配置导入的多项兼容性问题

- 引入 serde_path_to_error，反序列化失败时返回精确字段路径
- 为所有浮点字段新增数字字符串兼容反序列化器，支持 Python 序列化格式
- 修复 OAuth provider key 导入：正确写入加密的 api_key 和 auth_config
- 优化代理节点跳过提示，区分手动 URL 代理与 node_id 引用代理
- 新增测试覆盖上述场景

apps/aether-gateway/src/handlers/admin/shared/payloads.rs

@@ -1,7 +1,34 @@
-use serde::de::DeserializeOwned;
+use serde::{de, de::DeserializeOwned, Deserialize};
 use serde_json::{Map, Value};
 use std::collections::BTreeMap;
 
+pub(crate) fn deserialize_optional_f64_from_number_or_string<'de, D>(
+    deserializer: D,
+) -> Result<Option<f64>, D::Error>
+where
+    D: serde::Deserializer<'de>,
+{
+    let value = Option::<Value>::deserialize(deserializer)?;
+    match value {
+        None | Some(Value::Null) => Ok(None),
+        Some(Value::Number(number)) => number
+            .as_f64()
+            .filter(|value| value.is_finite())
+            .map(Some)
+            .ok_or_else(|| de::Error::custom("expected a finite number")),
+        Some(Value::String(raw)) => raw
+            .trim()
+            .parse::<f64>()
+            .ok()
+            .filter(|value| value.is_finite())
+            .map(Some)
+            .ok_or_else(|| de::Error::custom("expected a finite number or numeric string")),
+        Some(_) => Err(de::Error::custom(
+            "expected a finite number or numeric string",
+        )),
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub(crate) enum AdminJsonFieldState {
     Missing,