fix(PostImages, CreatePostScreen): adjust image gap for improved layout consistency

- Reduced image gap in PostImages and CreatePostScreen components from 12 to 4 (desktop) and 8 to 2 (mobile) for better spacing.
- Updated ImageGrid component to modify grid item widths for enhanced layout.
- Refactored PostRepository to improve local caching logic, ensuring non-blocking UI updates during cache writes.
- Introduced saveConversationsWithRelatedCache function to streamline conversation, user, and group data saving in the database.

src/stores/messageManager.ts

@@ -43,9 +43,7 @@ import {
   saveUserCache,
   updateMessageStatus,
   deleteConversation as deleteConversationFromDb,
-  saveConversationsCache,
-  saveUsersCache,
-  saveGroupsCache,
+  saveConversationsWithRelatedCache,
 } from '../services/database';
 import { api } from '../services/api';
 import { vibrateOnMessage } from '../services/messageVibrationService';
@@ -396,24 +394,17 @@ class MessageManager {
   /** 与会话列表同步写入本地缓存（参与者 / 群 / 列表） */
   private persistConversationListCache(): void {
     const list = Array.from(this.state.conversations.values());
-    saveConversationsCache(list).catch(error => {
+    const users = list.flatMap(conv => [
+      ...(conv.participants || []),
+      ...(conv.last_message?.sender ? [conv.last_message.sender] : []),
+    ]);
+    const groups = list
+      .map(conv => conv.group)
+      .filter((group): group is NonNullable<ConversationResponse['group']> => Boolean(group));
+    
+    saveConversationsWithRelatedCache(list, users, groups).catch(error => {
       console.error('[MessageManager] 持久化会话列表失败:', error);
     });
-    saveUsersCache(
-      list.flatMap(conv => [
-        ...(conv.participants || []),
-        ...(conv.last_message?.sender ? [conv.last_message.sender] : []),
-      ])
-    ).catch(error => {
-      console.error('[MessageManager] 持久化会话相关用户失败:', error);
-    });
-    saveGroupsCache(
-      list
-        .map(conv => conv.group)
-        .filter((group): group is NonNullable<ConversationResponse['group']> => Boolean(group))
-    ).catch(error => {
-      console.error('[MessageManager] 持久化会话相关群组失败:', error);
-    });
   }
 
   private recomputeConversationTotalUnread(): void {