fix: 修复相册缩略图无法显示(dev 代理 + 前端兜底)

- vite: /uploads 代理指向源站根而非 /apnew 前缀,relative thumbnailUrl
  (/uploads/thumb…) 在 dev 下不再落到 SPA index.html
- BubbleImage: 新增 fallbackSrc 候选链,缩略图加载失败时自动回退到绝对
  thumbUrl/url,全部失败才显示占位符
- AlbumBubble / ImageLightbox: 缩略图传入绝对地址作为兜底

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/messageStream/bubbles/AlbumBubble.tsx

@@ -50,7 +50,8 @@ export function AlbumBubble({ post }: { post: Post }) {
                 }
               >
                 <BubbleImage
-                  src={att.thumbnailUrl ?? att.url}
+                  src={att.thumbnailUrl ?? att.thumbUrl ?? att.url}
+                  fallbackSrc={[att.thumbUrl, att.url]}
                   loading="lazy"
                   className="h-full w-full object-cover transition duration-300 group-hover:scale-[1.03]"
                 />