fix(types): type handler as websocket handler in route() with websocket: true

[Tony133]

Proposal:

When using the full declaration syntax with websocket: true, handler is the websocket handler at runtime, but it was typed as a regular HTTP handler, so socket was inferred as FastifyRequest and request as FastifyReply. The shorthand methods already had a websocket: true overload; route() did not.

This adds the equivalent overload for route(), typing handler as WebsocketHandler when websocket: true, including generics and type provider inference.

Note:

• It is backwards compatible: routes with explicitly annotated HTTP handlers or with a wsHandler alongside websocket: true still compile as before. Rejecting wsHandler when websocket: true (it is ignored at runtime) could be a follow-up, but would be a breaking change for types.
• Added type tests for the new overload, with explicit generics and with TypeBox inference, plus a websocket: false route to make sure HTTP handlers are unchanged. The new assertions fail without the fix.

Fixes #314

[gurgunday]

lgtm

thanks!