feat(chat): enhance chat settings and message bubble styles

- Introduced dynamic chat settings for font size and message bubble radius, improving user customization.
- Updated ChatScreen styles to support dynamic themes and responsive layouts.
- Refactored bubble styles to utilize dynamic properties for better visual consistency.
- Simplified chat settings management by integrating Zustand store for state management.

This update significantly enhances the chat interface and user experience by allowing personalized settings and improved visual elements.

src/screens/auth/RegisterStep1Email.tsx

@@ -105,16 +105,16 @@ export const RegisterStep1Email: React.FC<RegisterStepProps> = ({
         <TouchableOpacity
           style={[
             styles.actionButton,
-            (sendingCode || countdown > 0) && styles.actionButtonDisabled,
+            (sendingCode || (countdown ?? 0) > 0) && styles.actionButtonDisabled,
           ]}
           onPress={handleSendCode}
-          disabled={sendingCode || countdown > 0}
+          disabled={sendingCode || (countdown ?? 0) > 0}
           activeOpacity={0.9}
         >
           <Text style={styles.actionButtonText}>
             {sendingCode
               ? '发送中...'
-              : countdown > 0
+              : (countdown ?? 0) > 0
               ? `${countdown}秒后重试`
               : '获取验证码'}
           </Text>