fix: implement MCP Streamable HTTP protocol for Cursor integration

- Replace basic JSON-RPC implementation with Streamable HTTP protocol
- Add support for GET (SSE) and POST (JSON-RPC) requests
- Update protocol version from 2024-11-05 to 2025-03-26
- Fix list_feeds tool definition to match actual API (remove unused page/pageSize params)
- Add ping method support for MCP Inspector
- Update Cursor configuration to use url field instead of curl command
- Add comprehensive MCP integration documentation

Fixes #32

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

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

routes.go

@@ -20,8 +20,8 @@ func setupRoutes(appServer *AppServer) *gin.Engine {
 	// 健康检查
 	router.GET("/health", healthHandler)
 
-	// MCP 端点 - 使用 SSE 协议
-	mcpHandler := appServer.createMCPHandler()
+	// MCP 端点 - 使用 Streamable HTTP 协议
+	mcpHandler := appServer.StreamableHTTPHandler()
 	router.Any("/mcp", gin.WrapH(mcpHandler))
 	router.Any("/mcp/*path", gin.WrapH(mcpHandler))