Fix remaining compilation errors: null-safety, removed packages, and nullable handling

- Fix AppState: remove removed connectivity package, fix imports (latlong2), make nullable fields optional
- Fix User model: use const empty strings in const constructor instead of null
- Fix model builders: add required ObjectId parameters to YourLocation and FireNotification
- Implement Comparable instead of extending it for BasicLocation
- Fix nullable callback handling in appActions and middleware (Completer<Null>?)
- Add null checks for BuildContext in dialogs (fireAlert, homePage, etc.)
- Fix nullable scaffold state access using ?. operator (activeFires, fireNotificationList)
- Handle nullable FireNotification and YourLocation in genericMapBottom
- Fix list type casting for widgets that can be null (<Widget?> with filtering)
- Add ObjectId imports where needed for model creation
- Fix Key? nullable parameter in introPage
- Add required parameters to markdownPage and slider constructors
- Remove connectivity-related code and imports (package removed)
- Handle nullable Completer in fetchDataMiddleware

All 104 errors resolved. 0 errors, 61 warnings/info remaining.

lib/supportPage.dart

@@ -1,6 +1,6 @@
 import 'package:comunes_flutter/comunes_flutter.dart';
 import 'package:flutter/material.dart';
-import 'package:launch_review/launch_review.dart';
+import 'package:in_app_review/in_app_review.dart';
 import 'package:url_launcher/url_launcher.dart';
 import 'package:share_plus/share_plus.dart';
 
@@ -20,7 +20,7 @@ class _SupportPageState extends State<SupportPage> {
   Widget buildSupportButton() {
     return new Align(
       alignment: const Alignment(0.0, -0.2),
-      child: new OutlineButton.icon(
+      child: new OutlinedButton.icon(
         icon: const Icon(Icons.favorite_border),
         label: new Text(S.of(context).comunesSupportBtn),
         onPressed: () {
@@ -33,11 +33,12 @@ class _SupportPageState extends State<SupportPage> {
   Widget buildShareButton() {
     return new Align(
       alignment: const Alignment(0.0, -0.2),
-      child: new OutlineButton.icon(
+      child: new OutlinedButton.icon(
         icon: const Icon(Icons.share),
         label: new Text(S.of(context).shareAppBtn),
         onPressed: () {
-          Share.shareWithResult('https://play.google.com/store/apps/details?id=org.comunes.fires');
+          Share.shareWithResult(
+              'https://play.google.com/store/apps/details?id=org.comunes.fires');
         },
       ),
     );
@@ -46,11 +47,11 @@ class _SupportPageState extends State<SupportPage> {
   Widget buildStarButton() {
     return new Align(
       alignment: const Alignment(0.0, -0.2),
-      child: new OutlineButton.icon(
+      child: new OutlinedButton.icon(
         icon: const Icon(Icons.star_border),
         label: new Text(S.of(context).starAppBtn),
         onPressed: () {
-          LaunchReview.launch();
+          InAppReview.instance.requestReview();
         },
       ),
     );
@@ -59,11 +60,12 @@ class _SupportPageState extends State<SupportPage> {
   Widget buildTranslateButton() {
     return new Align(
       alignment: const Alignment(0.0, -0.2),
-      child: new OutlineButton.icon(
+      child: new OutlinedButton.icon(
         icon: const Icon(Icons.translate),
         label: new Text(S.of(context).translateBtn),
         onPressed: () {
-          launch("https://translate.comunes.org/projects/todos-contra-el-fuego/");
+          launch(
+              "https://translate.comunes.org/projects/todos-contra-el-fuego/");
         },
       ),
     );