feat: add new fetch tool and related components

- Introduced a new fetch tool in `src/mastra/tools/fetch.tool.ts` for web content fetching and markdown conversion.
- Implemented various search functionalities including DuckDuckGo, Google, and Bing search.
- Added support for Google News RSS fetching.
- Included URL validation and sanitization to ensure safe fetching.
- Created a new React component for MCP A2A page in `app/chat/mcp-a2a/page.tsx` to manage MCP servers and tools.
- Developed a workspace management page in `app/chat/workspaces/page.tsx` to handle file browsing and skill display.
- Updated exports in `src/mastra/tools/index.ts` to include the new fetch tool.