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/components/Navbars/HomeNavbar.js

@@ -152,7 +152,7 @@ export default function HomeNavbar() {
                 borderColor={navbarBorder}
                 py={{ base: 2, md: 3 }}
             >
-                <Container maxW="container.xl" px={{ base: 3, md: 4 }} style={{ paddingRight: 'max(16px, env(safe-area-inset-right))' }}>
+                <Box px={{ base: 4, md: 6, lg: '80px' }}>
                     <Flex justify="space-between" align="center">
                         {/* Logo - 价小前投研 */}
                         <BrandLogo />
@@ -177,7 +177,7 @@ export default function HomeNavbar() {
                             followingEvents={followingEvents}
                         />
                     </Flex>
-                </Container>
+                </Box>
 
                 {/* 移动端抽屉菜单 (Phase 5 优化) */}
                 <MobileDrawer