Add backend status timestamp endpoint

backend/internal/httpx/router.go

@@ -2,6 +2,7 @@ package httpx
 
 import (
 	"net/http"
+	"time"
 
 	"github.com/gin-gonic/gin"
 	"senlinai-agent/backend/internal/config"
@@ -33,6 +34,9 @@ func newRouter(cfg config.Config, tokenVerifier func(string) (uint, error), regi
 		c.JSON(http.StatusOK, gin.H{"status": "ok"})
 	})
 	api := router.Group("/api")
+	api.GET("/status", func(c *gin.Context) {
+		c.JSON(http.StatusOK, gin.H{"timestamp_ms": time.Now().UnixMilli()})
+	})
 	if tokenVerifier != nil {
 		api.Use(auth.RequireUser(tokenVerifier))
 	}

backend/internal/httpx/router_test.go

@@ -1,9 +1,11 @@
 package httpx
 
 import (
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/require"
@@ -32,6 +34,19 @@ func TestNewRouterRegistersFeatureRoutesUnderAPI(t *testing.T) {
 	require.JSONEq(t, `{"pong":true}`, rec.Body.String())
 }
 
+func TestAPIStatusReturnsChangingTimestampMillisecondsWithoutAuth(t *testing.T) {
+	router := NewProtectedRouter(config.Config{Env: "test"}, func(token string) (uint, error) {
+		return 0, http.ErrNoCookie
+	})
+
+	first := getStatusTimestamp(t, router)
+	time.Sleep(2 * time.Millisecond)
+	second := getStatusTimestamp(t, router)
+
+	require.Greater(t, first, int64(0))
+	require.Greater(t, second, first)
+}
+
 func TestRouterAddsCORSHeadersForLocalWebClient(t *testing.T) {
 	router := NewRouter(config.Config{Env: "test"}, testRegistrar{})
 	req := httptest.NewRequest(http.MethodGet, "/api/ping", nil)
@@ -69,3 +84,18 @@ func (testRegistrar) Register(router gin.IRouter) {
 		c.JSON(http.StatusOK, gin.H{"pong": true})
 	})
 }
+
+func getStatusTimestamp(t *testing.T, router http.Handler) int64 {
+	t.Helper()
+	req := httptest.NewRequest(http.MethodGet, "/api/status", nil)
+	rec := httptest.NewRecorder()
+
+	router.ServeHTTP(rec, req)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	var payload struct {
+		TimestampMS int64 `json:"timestamp_ms"`
+	}
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &payload))
+	return payload.TimestampMS
+}