chore: highlight select mode actions

lib/pages/chat/chat_app_bar_title.dart

@@ -23,7 +23,7 @@ class ChatAppBarTitle extends StatelessWidget {
       return Text(
         controller.selectedEvents.length.toString(),
         style: TextStyle(
-          color: Theme.of(context).colorScheme.tertiary,
+          color: Theme.of(context).colorScheme.onTertiaryContainer,
         ),
       );
     }

lib/pages/chat/chat_input_row.dart

@@ -37,6 +37,10 @@ class ChatInputRow extends StatelessWidget {
       );
     }
 
+    final selectedTextButtonStyle = TextButton.styleFrom(
+      foregroundColor: theme.colorScheme.onTertiaryContainer,
+    );
+
     return Row(
       crossAxisAlignment: CrossAxisAlignment.end,
       mainAxisAlignment: MainAxisAlignment.spaceBetween,
@@ -63,6 +67,7 @@ class ChatInputRow extends StatelessWidget {
                 SizedBox(
                   height: height,
                   child: TextButton(
+                    style: selectedTextButtonStyle,
                     onPressed: controller.forwardEventsAction,
                     child: Row(
                       children: <Widget>[
@@ -80,6 +85,7 @@ class ChatInputRow extends StatelessWidget {
                       ? SizedBox(
                           height: height,
                           child: TextButton(
+                            style: selectedTextButtonStyle,
                             onPressed: controller.replyAction,
                             child: Row(
                               children: <Widget>[
@@ -92,6 +98,7 @@ class ChatInputRow extends StatelessWidget {
                       : SizedBox(
                           height: height,
                           child: TextButton(
+                            style: selectedTextButtonStyle,
                             onPressed: controller.sendAgainAction,
                             child: Row(
                               children: <Widget>[

lib/pages/chat/chat_view.dart

@@ -174,15 +174,18 @@ class ChatView extends StatelessWidget {
                 actionsIconTheme: IconThemeData(
                   color: controller.selectedEvents.isEmpty
                       ? null
-                      : theme.colorScheme.tertiary,
+                      : theme.colorScheme.onTertiaryContainer,
                 ),
+                backgroundColor: controller.selectedEvents.isEmpty
+                    ? null
+                    : theme.colorScheme.tertiaryContainer,
                 automaticallyImplyLeading: false,
                 leading: controller.selectMode
                     ? IconButton(
                         icon: const Icon(Icons.close),
                         onPressed: controller.clearSelectedEvents,
                         tooltip: L10n.of(context).close,
-                        color: theme.colorScheme.tertiary,
+                        color: theme.colorScheme.onTertiaryContainer,
                       )
                     : FluffyThemes.isColumnMode(context)
                         ? null
@@ -308,7 +311,9 @@ class ChatView extends StatelessWidget {
                               alignment: Alignment.center,
                               child: Material(
                                 clipBehavior: Clip.hardEdge,
-                                color: theme.colorScheme.surfaceContainerHigh,
+                                color: controller.selectedEvents.isNotEmpty
+                                    ? theme.colorScheme.tertiaryContainer
+                                    : theme.colorScheme.surfaceContainerHigh,
                                 borderRadius: const BorderRadius.all(
                                   Radius.circular(24),
                                 ),