Add RTSP Stream Support for Video Element

As a CMS User, I want to embed RTSP video streams in signage layouts so that I can display live broadcast feeds on screens.

Acceptance Criteria:

• Given I am editing a layout, when I add a video element, then I should be able to input an RTSP stream URL.

• Given an RTSP stream URL is entered, then the system should validate the format and check availability.

• Given the player supports RTSP, then the stream should play live in preview and on deployed screens.

• Given RTSP is not supported on certain player types, then the UI should provide a compatibility warning.

• Given the stream fails to load, then a fallback message or image should be shown.

• Support for basic authentication within the RTSP URL.

• RTSP playback should not interrupt or delay other media elements on the layout.