refactor(layout): 统一页面边距管理，移除 Container 限制

- layoutConfig.js: 新增 LAYOUT_PADDING 常量 { base: 4, md: 6, lg: '80px' }
- MainLayout.js: 在 Outlet 容器上统一应用 px={LAYOUT_PADDING.x}
- HomeNavbar.js: 边距从 lg:8 改为 lg:'80px'，与内容区对齐
- AppFooter.js: 移除 Container，边距改为 lg:'80px'

页面组件清理（移除冗余的 px/Container）：
- Company, Community, Center, Profile, Settings
- ValueForum, DataBrowser, LimitAnalyse, StockOverview, Concept

特殊处理：
- CompanyHeader: 使用负边距实现全宽背景
- Concept Hero: 使用负边距实现全宽背景

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

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

src/layouts/AppFooter.js

@@ -1,5 +1,5 @@
 import React from 'react';
-import { Box, Container, VStack, HStack, Text, Link, useColorModeValue } from '@chakra-ui/react';
+import { Box, VStack, HStack, Text, Link, useColorModeValue } from '@chakra-ui/react';
 import RiskDisclaimer from '../components/RiskDisclaimer';
 
 /**
@@ -8,8 +8,7 @@ import RiskDisclaimer from '../components/RiskDisclaimer';
  */
 const AppFooter = () => {
   return (
-    <Box bg={useColorModeValue('gray.100', 'gray.800')} py={2}>
-      <Container maxW="container.xl">
+    <Box bg={useColorModeValue('gray.100', 'gray.800')} py={2} px={{ base: 4, md: 6, lg: '80px' }}>
         <VStack spacing={1}>
           <RiskDisclaimer />
           <Text color="gray.500" fontSize="sm">
@@ -32,7 +31,6 @@ const AppFooter = () => {
             </Link>
           </HStack>
         </VStack>
-      </Container>
     </Box>
   );
 };