fix: revert health endpoint to /api/health (not /v1, per Coolify docs)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

rest/controllers/coolify_controller.go

@@ -120,7 +120,7 @@ func CoolifyTestConnection(c *fiber.Ctx) error {
 	}
 	base := strings.TrimRight(cfg.BaseURL, "/")
 	client := &http.Client{Timeout: 10 * time.Second}
-	resp, err := client.Get(base + "/api/v1/healthcheck")
+	resp, err := client.Get(base + "/api/health")
 	if err != nil {
 		return c.Status(fiber.StatusBadGateway).JSON(fiber.Map{"error": err.Error()})
 	}