feat(business): implement block-based content editing and rich text rendering

Introduce a new `BlockEditor` component and upgrade the post/message
rendering system to support rich text segments (images, @mentions,
votes, and post references).

- Implement `BlockEditor` for long-form post creation with image
  embedding support.
- Upgrade `PostContentRenderer` and `SegmentRenderer` to handle
  complex segment types including inline images and block elements.
- Refactor `PostCard` to use segment-based content and image
  signatures for optimized memoization.
- Centralize segment partitioning logic in `segmentUtils.ts` to ensure
  consistent rendering across chat and post modules.
- Update `PostRepository` and `Post` entity to support the new
  `segments` data structure.

src/screens/home/PostDetailScreen.tsx

@@ -1125,11 +1125,12 @@ export const PostDetailScreen: React.FC = () => {
                 lineHeight: isDesktop ? 32 : isTablet ? 30 : 28
               }
             ]}
+            onImagePress={(url) => handleImagePress([{ uri: url }], 0)}
           />
         </View>
 
-        {/* 图片 - 详情页显示所有图片，不限制数量 */}
-        {postImages.length > 0 && (
+        {/* 仅当 segments 中不含 image 时才渲染独立的图片区域 */}
+        {!post.segments?.some(s => s.type === 'image') && postImages.length > 0 && (
           <ImageGrid
             images={postImages}
             mode="auto"