feat: expose Fiber v3 Ctx methods on Request and rewrite webserver docs

- Add BodyRaw, Queries, FullURL, HasBody, HasHeader, IsFromLocal, Drop,
  Port, Referer, MediaType, Charset, Bind, XML, AutoFormat, SendStream
  wrappers to *Request (fiber.context.go)
- Fix All() to return fiber.Router instead of void (fiber.evo.go)
- Add ShutdownWithTimeout, ShutdownWithContext, GetRoutes to package
  level (fiber.evo.go)
- Fully rewrite docs/webserver.md to cover Fiber v3 and all evo features

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: getevo