fix: 注册 PUT /api/manager/settings 使设置保存生效

server.go NewServeMux 按方法分发到 handleSettingsPut（原仅注册 GET，PUT 静默返回旧值）

新增 TestSettingsPutRoundTrip 回归测试；gofmt 清理历史格式问题

internal/httpapi/server_test.go

@@ -97,3 +97,44 @@ func TestCanvasRoundTrip(t *testing.T) {
 		t.Fatalf("remotes after reload = %+v", got2.Remotes)
 	}
 }
+
+func TestSettingsPutRoundTrip(t *testing.T) {
+	_, ts := newTestHandler(t)
+	client := ts.Client()
+
+	// PUT updated settings
+	body := `{"autoStartProfiles":false,"restartOnExit":false,"restartIntervalSeconds":12}`
+	req, _ := http.NewRequest(http.MethodPut, ts.URL+"/api/manager/settings", bytes.NewBufferString(body))
+	req.SetBasicAuth("admin", "pw")
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("PUT settings status = %d, want 200", resp.StatusCode)
+	}
+
+	// Confirm response body reflects saved values
+	var saved store.Settings
+	if err := json.NewDecoder(resp.Body).Decode(&saved); err != nil {
+		t.Fatal(err)
+	}
+	if saved.AutoStartProfiles || saved.RestartOnExit || saved.RestartIntervalSeconds != 12 {
+		t.Fatalf("saved settings = %+v", saved)
+	}
+
+	// GET again to confirm persistence
+	req2, _ := http.NewRequest(http.MethodGet, ts.URL+"/api/manager/settings", nil)
+	req2.SetBasicAuth("admin", "pw")
+	resp2, err2 := client.Do(req2)
+	if err2 != nil {
+		t.Fatal(err2)
+	}
+	defer resp2.Body.Close()
+	var got store.Settings
+	_ = json.NewDecoder(resp2.Body).Decode(&got)
+	if got.AutoStartProfiles || got.RestartOnExit || got.RestartIntervalSeconds != 12 {
+		t.Fatalf("settings after reload = %+v", got)
+	}
+}