chore: Follow up appbar design

lib/pages/chat/chat_view.dart

@@ -254,10 +254,11 @@ class ChatView extends StatelessWidget {
                                     bottomRight:
                                         Radius.circular(AppConfig.borderRadius),
                                   ),
-                                  elevation: 6,
+                                  elevation: 4,
                                   shadowColor: Theme.of(context)
-                                      .dividerColor
-                                      .withAlpha(100),
+                                      .colorScheme
+                                      .onBackground
+                                      .withAlpha(64),
                                   clipBehavior: Clip.hardEdge,
                                   color: Theme.of(context).brightness ==
                                           Brightness.light

lib/pages/chat/events/message.dart

@@ -172,9 +172,9 @@ class Message extends StatelessWidget {
               padding: const EdgeInsets.only(left: 8),
               child: Material(
                 color: noBubble ? Colors.transparent : color,
-                elevation: event.type == EventTypes.Sticker ? 0 : 6,
+                elevation: event.type == EventTypes.Sticker ? 0 : 4,
                 shadowColor:
-                    Theme.of(context).secondaryHeaderColor.withAlpha(100),
+                    Theme.of(context).colorScheme.onBackground.withAlpha(64),
                 borderRadius: borderRadius,
                 clipBehavior: Clip.antiAlias,
                 child: InkWell(

lib/pages/chat_list/chat_list_header.dart

@@ -46,8 +46,9 @@ class ChatListHeader extends StatelessWidget implements PreferredSizeWidget {
                     topLeft: Radius.circular(AppConfig.borderRadius),
                     topRight: Radius.circular(AppConfig.borderRadius),
                   ),
-                  elevation: 6,
-                  shadowColor: Theme.of(context).dividerColor.withAlpha(100),
+                  elevation: 4,
+                  shadowColor:
+                      Theme.of(context).colorScheme.onBackground.withAlpha(64),
                   child: TextField(
                     controller: controller.searchController,
                     textInputAction: TextInputAction.search,