style(Community): 移除实时要闻与Footer之间的黑色空白区域

- Community/index.js: 移除 minH="100vh"，添加 flex="1" 填满父容器
- Community/index.js: 移除底部 padding (pb={{ base: 4, md: 8 }} → pb={0})
- DynamicNewsCard.js: 移除底部 margin (mb={4} → mb={0})

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/views/Community/components/DynamicNews/DynamicNewsCard.js

@@ -668,7 +668,7 @@ const [currentMode, setCurrentMode] = useState('vertical');
       {...rest}
       bg={cardBg}
       borderColor={borderColor}
-      mb={4}
+      mb={0}
       position="relative"
       zIndex={1}
       animation="fadeInUp 0.8s ease-out 0.2s both"

src/views/Community/index.js

@@ -149,9 +149,9 @@ const Community = () => {
   }, [location.pathname, registerEventUpdateCallback]); // 依赖路由变化重新注册
 
   return (
-    <Box minH="100vh" bg={bgColor}>
+    <Box bg={bgColor} flex="1">
       {/* 主内容区域 - padding 由 MainLayout 统一设置 */}
-      <Box ref={containerRef} pt={0} pb={{ base: 4, md: 8 }}>
+      <Box ref={containerRef} pt={0} pb={0}>
         {/* ⚡ 顶部说明面板（懒加载）：产品介绍 + 沪深指数 + 热门概念词云 */}
         <Suspense fallback={
           <Box mb={6} p={4} borderRadius="xl" bg="rgba(255,255,255,0.02)">