feat: add channel support

backend/src/main/java/com/openisle/config/ChannelInitializer.java

@@ -0,0 +1,32 @@
+package com.openisle.config;
+
+import com.openisle.model.MessageConversation;
+import com.openisle.repository.MessageConversationRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.stereotype.Component;
+
+@Component
+@RequiredArgsConstructor
+public class ChannelInitializer implements CommandLineRunner {
+    private final MessageConversationRepository conversationRepository;
+
+    @Override
+    public void run(String... args) {
+        if (conversationRepository.countByChannelTrue() == 0) {
+            MessageConversation chat = new MessageConversation();
+            chat.setChannel(true);
+            chat.setName("吹水群");
+            chat.setDescription("吹水聊天");
+            chat.setAvatar("/default-avatar.svg");
+            conversationRepository.save(chat);
+
+            MessageConversation tech = new MessageConversation();
+            tech.setChannel(true);
+            tech.setName("技术讨论群");
+            tech.setDescription("讨论技术相关话题");
+            tech.setAvatar("/default-avatar.svg");
+            conversationRepository.save(tech);
+        }
+    }
+}