feat(help): 重构帮助系统为图片渲染模式

添加浏览器管理器和图片管理器，用于通过 Playwright 渲染帮助菜单为图片
重构命令管理器以支持图片缓存和同步功能
添加 HTML 模板用于帮助菜单渲染

core/managers/browser_manager.py

@@ -0,0 +1,72 @@
+"""
+浏览器管理器模块
+
+负责管理全局唯一的 Playwright 浏览器实例，避免频繁启动/关闭浏览器的开销。
+"""
+import asyncio
+from typing import Optional
+from playwright.async_api import async_playwright, Browser, Playwright, Page
+from ..utils.logger import logger
+
+class BrowserManager:
+    """
+    浏览器管理器（异步单例）
+    """
+    _instance = None
+    _playwright: Optional[Playwright] = None
+    _browser: Optional[Browser] = None
+
+    def __new__(cls):
+        if cls._instance is None:
+            cls._instance = super().__new__(cls)
+        return cls._instance
+
+    async def initialize(self):
+        """
+        初始化 Playwright 和 Browser
+        """
+        if self._browser is None:
+            try:
+                logger.info("正在启动无头浏览器...")
+                self._playwright = await async_playwright().start()
+                # 启动 Chromium，headless=True 表示无头模式
+                self._browser = await self._playwright.chromium.launch(headless=True)
+                logger.success("无头浏览器启动成功！")
+            except Exception as e:
+                logger.exception(f"无头浏览器启动失败: {e}")
+                self._browser = None
+
+    async def get_new_page(self) -> Optional[Page]:
+        """
+        获取一个新的页面 (Page)
+        
+        使用完毕后，调用者应该负责关闭该页面 (await page.close())
+        """
+        if self._browser is None:
+            logger.warning("浏览器尚未初始化，尝试重新初始化...")
+            await self.initialize()
+            
+        if self._browser:
+            try:
+                return await self._browser.new_page()
+            except Exception as e:
+                logger.error(f"创建新页面失败: {e}")
+                return None
+        return None
+
+    async def shutdown(self):
+        """
+        关闭浏览器和 Playwright
+        """
+        if self._browser:
+            await self._browser.close()
+            self._browser = None
+            logger.info("浏览器已关闭")
+            
+        if self._playwright:
+            await self._playwright.stop()
+            self._playwright = None
+            logger.info("Playwright 已停止")
+
+# 全局浏览器管理器实例
+browser_manager = BrowserManager()