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

src/server/checker/engine.ts

@@ -12,7 +12,7 @@ export class ProbeEngine {
   private retentionMs: number;
   private semaphore: Semaphore;
   private store: ProbeStore;
-  private targetNameToId = new Map<string, number>();
+  private targetIds = new Set<string>();
   private targets: ResolvedTargetBase[];
   private timers: Array<ReturnType<typeof setInterval>> = [];
 
@@ -77,7 +77,7 @@ export class ProbeEngine {
           failure: errorFailure("internal", "engine", formatReason(result.reason)),
           matched: false,
           statusDetail: null,
-          targetName: target.name,
+          targetId: target.id,
           timestamp: new Date().toISOString(),
         });
       }
@@ -85,9 +85,9 @@ export class ProbeEngine {
   }
 
   private refreshCache(): void {
-    this.targetNameToId.clear();
+    this.targetIds.clear();
     for (const target of this.store.getTargets()) {
-      this.targetNameToId.set(target.name, target.id);
+      this.targetIds.add(target.id);
     }
   }
 
@@ -104,15 +104,14 @@ export class ProbeEngine {
   }
 
   private writeResult(result: CheckResult): void {
-    const targetId = this.targetNameToId.get(result.targetName);
-    if (!targetId) return;
+    if (!this.targetIds.has(result.targetId)) return;
 
     this.store.insertCheckResult({
       durationMs: result.durationMs,
       failure: result.failure,
       matched: result.matched,
       statusDetail: result.statusDetail,
-      targetId,
+      targetId: result.targetId,
       timestamp: result.timestamp,
     });
   }