Implement WebSocket Secure (WSS) UA transport

[marcschier]

Implement WebSocket Secure (WSS) UA transport

The OPC UA .NET Standard Stack currently does not support the WebSocket
Secure transport profile (opc.wss://,
http://opcfoundation.org/UA-Profile/Transport/uawss-uasc-uabinary),
even though the URI constant exists in
SecurityConstants.UaWssTransport.

Acceptance criteria

• Both client and server are able to negotiate and run an OPC UA
  session over opc.wss:// with UA Secure Conversation + binary
  encoding (the same UASC/UABinary pipeline as opc.tcp://).
• The reference server's Quickstarts.ReferenceServer.Config.xml
  exposes a WSS endpoint that the reference client and CTT can talk to.
• Integration tests cover handshake, message framing, server-cert /
  client-cert flows, large-chunk handling, and keep-alive.
• Docs/Profiles.md is updated to list the WSS transport profile as
  supported and the "Currently not supported" entry is removed.
• The CTT certification report covers the WSS profile.

Notes

• Tracked separately from the HTTPS-JSON transport (see companion
  issue).
• This may be implemented as a new binding assembly
  (Opc.Ua.Bindings.Wss) parallel to Opc.Ua.Bindings.Https.