Fix all code warnings

lib/ui/widgets/countdown_widget.dart

@@ -75,7 +75,7 @@ class _CountdownWidgetState extends State<CountdownWidget> {
               value: remainingTime <= 0
                   ? 1.0
                   : 1 - (remainingTime / totalDuration),
-              backgroundColor: Theme.of(context).accentColor,
+              backgroundColor: Theme.of(context).colorScheme.secondary,
               valueColor: AlwaysStoppedAnimation<Color>(
                   Theme.of(context).backgroundColor),
             ),

lib/ui/widgets/login_routes_theme.dart

@@ -43,7 +43,6 @@ class LoginRoutesTheme extends StatelessWidget {
             backgroundColor: Config.get().splashBackgroundColor,
             disabledColor: Colors.grey,
             highlightColor: Colors.white12,
-            accentColor: Colors.white,
             hintColor: Colors.white,
             textTheme: TextTheme(subtitle1: TextStyle(color: Colors.white)),
             radioTheme: RadioThemeData(
@@ -63,7 +62,7 @@ class LoginRoutesTheme extends StatelessWidget {
               onBackground: Colors.white,
               onError: Colors.redAccent,
               brightness: Brightness.dark,
-            )),
+            ).copyWith(secondary: Colors.white)),
         child: child,
       );
 }

lib/ui/widgets/tablet_mode/conversations/conversation_window_container.dart

@@ -44,7 +44,6 @@ class ConversationWindowContainer extends StatelessWidget {
           appBar: AppBarWrapper(
               height: 40,
               appBar: AppBar(
-                textTheme: TextTheme(headline6: TextStyle(fontSize: 15)),
                 backgroundColor: appBarBgColor,
                 leading: icon,
                 title: GestureDetector(child: title, onTap: onToggleCollapse),
@@ -52,6 +51,10 @@ class ConversationWindowContainer extends StatelessWidget {
                   ..add(
                     IconButton(icon: Icon(Icons.close), onPressed: onClose),
                   ),
+                toolbarTextStyle:
+                    TextTheme(headline6: TextStyle(fontSize: 15)).bodyText2,
+                titleTextStyle:
+                    TextTheme(headline6: TextStyle(fontSize: 15)).headline6,
               )),
           body: Visibility(
             child: body,

lib/ui/widgets/tablet_mode/user_page_tablet.dart

@@ -16,7 +16,6 @@ import 'package:comunic/utils/date_utils.dart';
 import 'package:comunic/utils/intl_utils.dart';
 import 'package:comunic/utils/ui_utils.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter/rendering.dart';
 
 /// Tablet mode of user page
 ///

lib/ui/widgets/text_rich_content_widget.dart

@@ -1,5 +1,3 @@
-import 'dart:ui';
-
 import 'package:comunic/utils/input_utils.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';