Fix 23 additional lint issues to reduce from 129 to 106 issues

- Add const constructors to @immutable classes (5 issues: prefer_const_constructors_in_immutables)
- Fix nullable value casts in firesApi.dart (3 issues: cast_nullable_to_non_nullable)
- Remove redundant default argument values (2 issues: avoid_redundant_argument_values)
- Make YourLocation immutable with final fields (2 issues: avoid_equals_and_hash_code_on_mutable_classes)
- Update imports and fix formatting

Reduces lint issues from 129 to 106. APK builds successfully (146 MB).

lib/widgets/app_intro_page.dart

@@ -6,25 +6,25 @@ import 'package:flutter/material.dart';
 import '../utils/widget_utils.dart';
 
 class AppIntroItem {
+  AppIntroItem({required this.icon, required this.title, this.subTitle = ''});
+
   final IconData icon;
   final String title;
   final String subTitle;
-
-  AppIntroItem({required this.icon, required this.title, this.subTitle = ''});
 }
 
 typedef void OnIntroFinish(BuildContext context);
 typedef List<AppIntroItem> ListItems(BuildContext context);
 
 abstract class AppIntroPage extends StatelessWidget {
-  static const String routeName = '/appintro';
-  final ListItems items;
-  final OnIntroFinish onIntroFinish;
-
   const AppIntroPage(
       {Key? key, required this.items, required this.onIntroFinish})
       : super(key: key);
 
+  static const String routeName = '/appintro';
+  final ListItems items;
+  final OnIntroFinish onIntroFinish;
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -63,7 +63,6 @@ class _AppIntroPageSelector extends StatelessWidget {
         theme.textTheme.titleMedium ?? const TextStyle();
 
     return SafeArea(
-      top: true,
       bottom: false,
       child: Column(
         children: <Widget>[
@@ -75,7 +74,8 @@ class _AppIntroPageSelector extends StatelessWidget {
                 icon:
                     const Icon(Icons.close, size: 30.0, color: Colors.black38)),
           ]),
-          Expanded(child: OrientationBuilder(builder: (context, orientation) {
+          Expanded(child: OrientationBuilder(
+              builder: (BuildContext context, Orientation orientation) {
             return IconTheme(
               data: IconThemeData(
                 size: orientation == Orientation.portrait ? 200.0 : 100.0,