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/widgets/mobile/mobile_set_password.dart

@@ -28,10 +28,10 @@ class MobileSetPasswordState extends State<MobileSetPassword> {
   final passwordController = TextEditingController();
   final passwordAgainController = TextEditingController();
 
-  bool passwordVisible;
-  bool passwordAgainVisible;
+  late bool passwordVisible;
+  late bool passwordAgainVisible;
 
-  bool canReset;
+  late bool canReset;
 
   @override
   void initState() {
@@ -106,7 +106,7 @@ class MobileSetPasswordState extends State<MobileSetPassword> {
                         fontSize: 18.0
                     ),
                     validator: (String? value) {
-                      if (value.trim().isEmpty) {
+                      if (value!.trim().isEmpty) {
                         return S.of(context).password_is_required;
                       }
                       return null;
@@ -160,10 +160,10 @@ class MobileSetPasswordState extends State<MobileSetPassword> {
                         fontSize: 18.0
                     ),
                     validator: (String? value) {
-                      if (value.trim().isEmpty) {
+                      if (value!.trim().isEmpty) {
                         return S.of(context).password_is_required;
                       }
-                      if (value.trim() != passwordController.text.trim()) {
+                      if (value!.trim() != passwordController.text.trim()) {
                         return S.of(context).password_is_not_match_password_again;
                       }
                       return null;