feat(health-check): enhance HTTP probe functionality with URL helpers

Added new utility functions `hostForUrl` and `buildHttpProbeUrl` to improve URL construction for health checks. Updated `httpProbe` to utilize these functions, ensuring proper handling of FQDN and IP addresses. Enhanced tests to validate the new URL building logic and ensure correct behavior with different hostnames and IPs.

apps/api/test/health-check.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it, beforeAll, afterAll } from "vitest";
 import { createServer, type Server } from "node:net";
+import { createServer as createHttpServer, type Server as HttpServer } from "node:http";
 import * as healthCheckService from "../src/services/health-check-service.js";
 import type { HealthCheckTarget } from "@cfdm/shared";
 
@@ -15,6 +16,20 @@ function startTcpServer(): Promise<{ server: Server; port: number }> {
   });
 }
 
+describe("health-check URL helpers", () => {
+  it("buildHttpProbeUrl uses FQDN in URL (IP pinned via DNS interceptor)", () => {
+    expect(
+      healthCheckService.buildHttpProbeUrl("gt.rkns.top", 443, "/", true),
+    ).toBe("https://gt.rkns.top/");
+    expect(
+      healthCheckService.buildHttpProbeUrl("gt.rkns.top", 8080, "/health", false),
+    ).toBe("http://gt.rkns.top:8080/health");
+    expect(
+      healthCheckService.buildHttpProbeUrl("2001:db8::1", 443, "/", true),
+    ).toBe("https://[2001:db8::1]/");
+  });
+});
+
 describe("health-check probeTarget", () => {
   let server: Server;
   let port: number;
@@ -63,6 +78,53 @@ describe("health-check probeTarget", () => {
     expect(result.ok).toBe(false);
     expect(result.error).not.toBeNull();
   });
+
+  it("http probe hits IP with Host=hostname (same IP, different FQDN)", async () => {
+    let seenHost: string | undefined;
+    const httpServer: HttpServer = createHttpServer((req, res) => {
+      seenHost = req.headers.host;
+      res.writeHead(200);
+      res.end("ok");
+    });
+    const httpPort = await new Promise<number>((resolve) => {
+      httpServer.listen(0, "127.0.0.1", () => {
+        const address = httpServer.address();
+        resolve(typeof address === "object" && address ? address.port : 0);
+      });
+    });
+
+    try {
+      const groupTarget: HealthCheckTarget = {
+        scope: "group",
+        ref_id: 1,
+        ip: "127.0.0.1",
+        hostname: "gt.rkns.top",
+        type: "http",
+        port: httpPort,
+        path: "/",
+        expected_status: 200,
+        timeout_ms: 1000,
+      };
+      const bindingTarget: HealthCheckTarget = {
+        ...groupTarget,
+        scope: "binding",
+        hostname: "rutg.rkns.top",
+      };
+
+      const groupResult = await healthCheckService.probeTarget(groupTarget);
+      expect(groupResult.ok).toBe(true);
+      expect(seenHost?.startsWith("gt.rkns.top")).toBe(true);
+
+      const bindingResult = await healthCheckService.probeTarget(bindingTarget);
+      expect(bindingResult.ok).toBe(true);
+      expect(seenHost?.startsWith("rutg.rkns.top")).toBe(true);
+
+      // Same loopback IP → latencies in the same ballpark (not ~1s DNS skew)
+      expect(Math.abs(groupResult.latencyMs - bindingResult.latencyMs)).toBeLessThan(200);
+    } finally {
+      await new Promise<void>((resolve) => httpServer.close(() => resolve()));
+    }
+  });
 });
 
 describe("health-check state derivation via runAllChecks", () => {
@@ -90,7 +152,6 @@ describe("health-check state derivation via runAllChecks", () => {
       { ip: "127.0.0.1", weight: 1, priority: 1 },
     ]);
 
-    // Запуск с closed port (port 1) — должен зафиксировать down после 2 проверок
     await healthCheckService.runAllChecks(db, {
       thresholds: {
         degradedFailures: 1,