fix: 修复中国地图页面搜索栏不显示的问题

- 简化header布局结构，移除flex-col导致的布局问题
- 使用统一的水平flex布局：左侧(返回/Logo)、中间(搜索)、右侧(区域)
- 改用 style.display 直接控制显示隐藏，更可靠
- 优化响应式布局，确保PC端搜索框正常显示

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

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

js/ui/MapInterface.js

@@ -93,12 +93,11 @@ export class MapInterface {
             document.getElementById('breadcrumb-container').classList.add('hidden');
             const backBtn = document.getElementById('map-back-btn');
             if (backBtn) {
-                backBtn.classList.add('hidden');
-                backBtn.classList.remove('flex');
+                backBtn.style.display = 'none';
             }
             const logoArea = document.getElementById('map-logo-area');
             if (logoArea) {
-                logoArea.classList.remove('hidden');
+                logoArea.style.display = 'flex';
             }
             
             document.getElementById('top-region-name').innerText = '全国';
@@ -124,12 +123,11 @@ export class MapInterface {
                 // 显示返回按钮，隐藏logo
                 const backBtn = document.getElementById('map-back-btn');
                 if (backBtn) {
-                    backBtn.classList.remove('hidden');
-                    backBtn.classList.add('flex');
+                    backBtn.style.display = 'flex';
                 }
                 const logoArea = document.getElementById('map-logo-area');
                 if (logoArea) {
-                    logoArea.classList.add('hidden');
+                    logoArea.style.display = 'none';
                 }
                 
                 document.getElementById('top-region-name').innerText = provinceInfo.name;