#1178 Support for route parameters in WebSocket onaccept handlers

[jwolak]

Refers to #1178

Add support parameterized routes like:
/ws/<int>
/ws/<string>
/ws/<path>
and pass the parsed values directly into the onaccept callback, e.g.:

CROW_WEBSOCKET_ROUTE(app, "/ws/<int>")
  .onaccept([](const crow::request&, std::optional<crow::response>&, void**, int64_t id) {
      // id == parsed route parameter
  });

This makes WebSocket route logic consistent with the rest of Crow’s routing system and enables request-specific validation or connection setup based on URL parameters.

The change also supports bool-returning onaccept handlers, where returning false rejects the upgrade with a 400 response, and includes unit tests covering int, uint, double, string, path, and rejection cases.