refactor: Migrate to Flutter 3.7.0

lib/pages/chat/events/cute_events.dart

@@ -69,7 +69,7 @@ class _CuteContentState extends State<CuteContent> {
         },
       ),
     );
-    Overlay.of(context)?.insert(overlay);
+    Overlay.of(context).insert(overlay);
   }
 
   generateLabel(User? user) {

lib/pages/chat/events/html_message.dart

@@ -52,7 +52,7 @@ class HtmlMessage extends StatelessWidget {
       defaultTextStyle: defaultTextStyle,
       emoteSize: emoteSize,
       linkStyle: linkStyle ??
-          themeData.textTheme.bodyText2!.copyWith(
+          themeData.textTheme.bodyMedium!.copyWith(
             color: themeData.colorScheme.secondary,
             decoration: TextDecoration.underline,
           ),

lib/pages/chat/events/message.dart

@@ -303,8 +303,11 @@ class Message extends StatelessWidget {
               child: Center(
                   child: Material(
                 color: displayTime
-                    ? Theme.of(context).backgroundColor
-                    : Theme.of(context).backgroundColor.withOpacity(0.33),
+                    ? Theme.of(context).colorScheme.background
+                    : Theme.of(context)
+                        .colorScheme
+                        .background
+                        .withOpacity(0.33),
                 borderRadius: BorderRadius.circular(AppConfig.borderRadius / 2),
                 clipBehavior: Clip.antiAlias,
                 child: Padding(

lib/pages/chat/events/verification_request_content.dart

@@ -37,7 +37,7 @@ class VerificationRequestContent extends StatelessWidget {
               color: Theme.of(context).dividerColor,
             ),
             borderRadius: BorderRadius.circular(AppConfig.borderRadius),
-            color: Theme.of(context).backgroundColor,
+            color: Theme.of(context).colorScheme.background,
           ),
           child: Row(
             mainAxisSize: MainAxisSize.min,