phase3: nullfix.py batch script — bang/late/param-nullable

Automated null-safety fixes driven by dart analyze (no corruption):
- unchecked_use_of_nullable_value: insert '!' on receiver (property/method/[]/op)
- not_initialized field/var: mark 'late'
- missing_default_value_for_parameter: nullable param
Errors: 2374(peak) -> 907

lib/pages/buy_service.dart

@@ -30,7 +30,7 @@ class BuyService extends StatefulWidget {
 }
 
 class BuyServiceState extends State<BuyService> {
-  Map<String, dynamic> data;
+  late Map<String, dynamic> data;
 
   @override
   Widget build(BuildContext context) {

lib/pages/contact_us.dart

@@ -22,7 +22,7 @@ class ContactUs extends StatefulWidget {
 }
 
 class ContactUsState extends State<ContactUs> {
-  Business business;
+  late Business business;
 
   @override
   Widget build(BuildContext context) {

lib/pages/download.dart

@@ -30,7 +30,7 @@ class Download extends StatefulWidget {
 
 class DownloadState extends State<Download> {
   final _scaffoldKey = GlobalKey<ScaffoldState>();
-  Map<String, dynamic> data;
+  late Map<String, dynamic> data;
 
   @override
   Widget build(BuildContext context) {
@@ -79,7 +79,7 @@ class DownloadState extends State<Download> {
     super.initState();
     eventBus.on<OpenDrawer>().listen((event) {
       if (mounted) {
-        _scaffoldKey.currentState.openDrawer();
+        _scaffoldKey.currentState!.openDrawer();
       }
     });
     _loadData();

lib/pages/igoshow_learn_more.dart

@@ -26,7 +26,7 @@ class IGoShowLearnMore extends StatefulWidget {
 
 class IGoShowLearnMoreState extends State<IGoShowLearnMore> {
   final _scaffoldKey = GlobalKey<ScaffoldState>();
-  Map<String, dynamic> data;
+  late Map<String, dynamic> data;
 
   @override
   Widget build(BuildContext context) {

lib/pages/minipos_learn_more.dart

@@ -26,7 +26,7 @@ class MiniPosLearnMore extends StatefulWidget {
 
 class MiniPosLearnMoreState extends State<MiniPosLearnMore> {
   final _scaffoldKey = GlobalKey<ScaffoldState>();
-  Map<String, dynamic> data;
+  late Map<String, dynamic> data;
 
   @override
   Widget build(BuildContext context) {

lib/pages/plain_page.dart

@@ -23,7 +23,7 @@ class PlainPage extends StatefulWidget {
 }
 
 class PlainPageState extends State<PlainPage> {
-  Blog blog;
+  late Blog blog;
 
   @override
   Widget build(BuildContext context) {

lib/pages/renew_minioffice.dart

@@ -25,7 +25,7 @@ class RenewMiniOffice extends StatefulWidget {
 }
 
 class RenewMiniOfficeState extends State<RenewMiniOffice> {
-  Map<String, dynamic> data;
+  late Map<String, dynamic> data;
 
   @override
   Widget build(BuildContext context) {