feat(auth): allow JWT IP changes by configuration (#1236)

* feat(auth): allow JWT IP changes by configuration

* fix(auth): make JWT IP change setting concurrency-safe

* test(auth): move JWT IP change setting tests out of MCP test file

cmd/dashboard/controller/setting_jwt_ip_change_test.go

@@ -0,0 +1,26 @@
+package controller
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/nezhahq/nezha/model"
+)
+
+func TestSettingForm_AllowJWTIPChangePreservesAbsentAndDecodesExplicitValues(t *testing.T) {
+	var omitted model.SettingForm
+	require.NoError(t, json.Unmarshal([]byte(`{"site_name":"X"}`), &omitted))
+	require.Nil(t, omitted.AllowJWTIPChange)
+
+	var enabled model.SettingForm
+	require.NoError(t, json.Unmarshal([]byte(`{"allow_jwt_ip_change":true}`), &enabled))
+	require.NotNil(t, enabled.AllowJWTIPChange)
+	require.True(t, *enabled.AllowJWTIPChange)
+
+	var disabled model.SettingForm
+	require.NoError(t, json.Unmarshal([]byte(`{"allow_jwt_ip_change":false}`), &disabled))
+	require.NotNil(t, disabled.AllowJWTIPChange)
+	require.False(t, *disabled.AllowJWTIPChange)
+}