handleRequest
Convert a serverless event into a standard Request, route it through the Hono
app, and return a normalized ServerlessResponse.
Parameters
app
A Hono-compatible application with a fetch method.
event
The incoming serverless event. Properties include httpMethod, method,
headers, body, path, rawPath, and queryStringParameters.
Returns
Promise<ServerlessResponse> — A normalized response with statusCode,
headers, and body.