Add ONVIF support for RTSP server mode

Scope (best‑effort Profile T):
      1. WS‑Discovery + XAddrs for Device Service
      2. Device Service: GetCapabilities, GetServices, GetDeviceInformation
      3. Media Service: GetProfiles, GetStreamUri (RTSP URL)
      4. Single fixed profile; no dynamic reconfiguration
      5. Optional auth; no TLS; explicitly not ONVIF‑conformant