feat: 配置变量系统与 target id/name 双字段标识

- 新增顶层 variables 段支持 string/number/boolean 字面量
- target 字符串字段支持 、、{...} 转义语法
- 变量解析优先级: variables -> process.env -> 默认值 -> 报错
- 完整引用保留原始类型，部分引用拼接为字符串
- 变量替换在 YAML 解析后、AJV 校验前执行
- 替换仅作用于 targets，跳过 id/type 字段
- target 新增必填 id 字段作为唯一标识，name 改为可选展示名称
- 数据库存储/API/前端全面迁移到 id 标识
- 统一 checker 运行时类型检查为 es-toolkit predicates
- 同步 delta specs 到主 specs，归档 config-variables 变更

tests/server/checker/config-contract/validate.test.ts

@@ -28,6 +28,7 @@ describe("config contract", () => {
         targets: [
           {
             http: { method: "get", unknownHttpField: true, url: "https://example.com" },
+            id: "api",
             name: "api",
             type: "http",
           },
@@ -36,6 +37,31 @@ describe("config contract", () => {
     ).toBe(false);
   });
 
+  test("导出 schema 支持 variables 且要求 target id", () => {
+    const ajv = new Ajv({
+      allErrors: true,
+      coerceTypes: false,
+      removeAdditional: false,
+      strict: true,
+      useDefaults: false,
+    });
+    const validate = ajv.compile(createProbeConfigJsonSchema(createDefaultCheckerRegistry()));
+
+    expect(
+      validate({
+        targets: [{ http: { url: "https://example.com" }, id: "api", type: "http" }],
+        variables: { base_url: "https://example.com", enabled: true, port: 443 },
+      }),
+    ).toBe(true);
+
+    expect(
+      validate({
+        targets: [{ http: { url: "https://example.com" }, type: "http" }],
+        variables: { bad: null },
+      }),
+    ).toBe(false);
+  });
+
   test("Ajv 错误转换为中文结构化 issue", () => {
     const result = validateProbeConfigContract(
       {
@@ -43,6 +69,7 @@ describe("config contract", () => {
           {
             group: 123,
             http: { extra: true },
+            id: "api",
             name: "api",
             type: "http",
           },