refactor(message): modularize MessageManager architecture

重构消息管理模块，将单体 MessageManager 拆分为职责单一的子模块：

- MessageStateManager: 纯状态管理
- MessageDeduplication: 消息去重服务
- UserCacheService: 用户缓存服务
- ReadReceiptManager: 已读回执管理
- ConversationOperations: 会话操作
- MessageSendService: 消息发送
- MessageSyncService: 消息同步
- WSMessageHandler: WebSocket 消息处理

新增类型定义和常量文件，保持原有 API 向后兼容。修复 CallScreen 状态值错误，补充 PostDetailScreen 缺失样式，优化 GroupInfoPanel 导入。

src/stores/message/MessageSendService.ts

@@ -0,0 +1,144 @@
+/**
+ * 消息发送服务
+ * 处理消息发送相关逻辑
+ */
+
+import type { MessageResponse, MessageSegment, ConversationResponse } from '../../types/dto';
+import { messageService } from '../../services/messageService';
+import { saveMessage } from '../../services/database';
+import type { IMessageSendService, IMessageStateManager } from './types';
+
+export class MessageSendService implements IMessageSendService {
+  private stateManager: IMessageStateManager;
+  private getCurrentUserId: () => string | null;
+
+  constructor(stateManager: IMessageStateManager, getCurrentUserId: () => string | null) {
+    this.stateManager = stateManager;
+    this.getCurrentUserId = getCurrentUserId;
+  }
+
+  /**
+   * 发送消息
+   */
+  async sendMessage(
+    conversationId: string,
+    segments: MessageSegment[],
+    options?: { replyToId?: string }
+  ): Promise<MessageResponse | null> {
+    try {
+      // 调用API发送
+      const response = await messageService.sendMessage(conversationId, {
+        segments,
+        reply_to_id: options?.replyToId,
+      });
+
+      if (response) {
+        const currentUserId = this.getCurrentUserId();
+        
+        // 添加到本地消息列表
+        const existingMessages = this.stateManager.getMessages(conversationId);
+        const newMessage: MessageResponse = {
+          id: response.id,
+          conversation_id: conversationId,
+          sender_id: currentUserId || '',
+          seq: response.seq,
+          segments,
+          created_at: new Date().toISOString(),
+          status: 'normal',
+        };
+
+        const updatedMessages = this.mergeMessagesById(existingMessages, [newMessage]);
+        this.stateManager.setMessages(conversationId, updatedMessages);
+
+        // 关键：立即广播消息列表更新
+        this.stateManager.notifySubscribers({
+          type: 'messages_updated',
+          payload: {
+            conversationId,
+            messages: updatedMessages,
+            newMessage,
+            source: 'send',
+          },
+          timestamp: Date.now(),
+        });
+
+        // 更新会话最后消息
+        this.updateConversationWithNewMessage(conversationId, newMessage);
+
+        // 通知消息已发送
+        this.stateManager.notifySubscribers({
+          type: 'message_sent',
+          payload: { conversationId, message: newMessage },
+          timestamp: Date.now(),
+        });
+
+        // 保存到本地数据库
+        const textContent = segments
+          ?.filter((s: any) => s.type === 'text')
+          .map((s: any) => s.data?.text || '')
+          .join('') || '';
+        
+        saveMessage({
+          id: response.id,
+          conversationId,
+          senderId: currentUserId || '',
+          content: textContent,
+          type: segments?.find((s: any) => s.type === 'image') ? 'image' : 'text',
+          isRead: true,
+          createdAt: newMessage.created_at,
+          seq: response.seq,
+          status: 'normal',
+          segments,
+        }).catch(console.error);
+
+        return newMessage;
+      }
+
+      return null;
+    } catch (error) {
+      console.error('[MessageSendService] 发送消息失败:', error);
+      this.stateManager.notifySubscribers({
+        type: 'error',
+        payload: { error, context: 'sendMessage' },
+        timestamp: Date.now(),
+      });
+      return null;
+    }
+  }
+
+  /**
+   * 更新会话的最后消息信息
+   */
+  private updateConversationWithNewMessage(
+    conversationId: string,
+    message: MessageResponse
+  ): void {
+    const conversation = this.stateManager.getConversation(conversationId);
+    const createdAt = message.created_at || new Date().toISOString();
+
+    if (conversation) {
+      // 更新现有会话
+      const updatedConv: ConversationResponse = {
+        ...conversation,
+        last_seq: message.seq,
+        last_message: message,
+        last_message_at: createdAt,
+        updated_at: createdAt,
+      };
+
+      this.stateManager.updateConversation(updatedConv);
+    }
+  }
+
+  /**
+   * 按 message_id 合并消息并按 seq 排序
+   */
+  private mergeMessagesById(base: MessageResponse[], incoming: MessageResponse[]): MessageResponse[] {
+    if (incoming.length === 0) return base;
+    const merged = new Map<string, MessageResponse>();
+    [...base, ...incoming].forEach(msg => {
+      merged.set(String(msg.id), msg);
+    });
+    return Array.from(merged.values()).sort((a, b) => a.seq - b.seq);
+  }
+}