refactor: switch mcp http to framework-agnostic McpHttpError

[hashemix]

📌 Summary

Switches the entire mcp_http/ layer (handler, middleware, utilities, types) from TransportServerError/TransportServerResult to the framework-agnostic McpHttpError/McpHttpResult types introduced in the prior PR.
This cuts all imports from hyper_servers/ and mcp_server::error out of the HTTP handler layer.

✨ Changes Made

• mcp_http/types.rs: GenericBody error type changed to McpHttpError; BoxFutureResponse and RequestHandler type aliases switched to McpHttpResult
• mcp_http/http_utils.rs: All TransportServerError/TransportServerResult → McpHttpError/McpHttpResult; dropped hyper_servers::error import
• mcp_http/mcp_http_handler.rs: All method return types and internal error construction switched to McpHttpError/McpHttpResult
• mcp_http/middleware.rs + 4 sub-modules: Middleware trait + all implementations switched
• auth/auth_provider.rs: AuthProvider trait return type switched to McpHttpError (cascaded from GenericBody change)
• auth/auth_provider/remote_auth_provider.rs: Internal methods and body construction switched
• rust-mcp-extra/src/auth_provider/{keycloak,scalekit,work_os}.rs: All three AuthProvider implementors updated to use McpHttpError/McpHttpResult

🛠️ Testing Steps

cargo make check