refactor: Enhance UI components with updated border styles and theme adjustments

- Removed unnecessary border from UserMessageBubble for a cleaner appearance.
- Adjusted Divider and OutlineInputBorder styles in ChatsDrawer to improve visual consistency with updated alpha values.
- Updated color tokens in AppColorTokens and TweakcnThemes to streamline theme management and ensure better contrast handling.
- Introduced new Tweakcn theme variant 'Claude' for a warm, tactile palette, enhancing overall UI aesthetics.

lib/features/chat/widgets/user_message_bubble.dart

@@ -499,11 +499,6 @@ class _UserMessageBubbleState extends ConsumerState<UserMessageBubble>
                           borderRadius: BorderRadius.circular(
                             AppBorderRadius.messageBubble,
                           ),
-                          border: Border.all(
-                            color: context.conduitTheme.chatBubbleUserBorder
-                                .withValues(alpha: 0.5),
-                            width: BorderWidth.standard,
-                          ),
                         ),
                         child: _isEditing
                             ? Focus(