Rewrite: SIP domain applications

[Manny-r31]

Rewrite: SIP domain applications (/platform/voice/sip/domain-applications)

Current state

• Source file: /signalwire-fern-config/fern/products/platform/pages/calling/voice/SIP/sip-domain-apps/index.mdx
• Live URL: https://signalwire.com/docs/platform/voice/sip/domain-applications
• Page type (Fern): overview
• Approx. length: 434 words / 102 lines

What's there today

• Intro paragraph explaining Domain Applications route SIP traffic to custom domains and reference a Dashboard handler setup; includes a screenshot of the Domain App page.
• RELAY Application section with dual-tab code examples (V4 and V3) showing how to listen for incoming calls on topics/contexts, with a note directing readers to the SDK reference.
• Video Room section covering immediate connection of inbound SIP calls to video rooms via the handler dropdown.
• Tip directing to a "help page" at /docs/platform/your-signalwire-api-space for "full guide to creating and configuring new Domain Applications."

Reviewer's concern

"Needs to be rewritten for SIP Credentials and the like."

We need to have a conversation, Ideally with Brian and/or Jerris present, on what to do with this page. With everyone being forced onto the new UI soon and off of legacy we will need to figure out whether we need to deprecate this and hide it, explain to users where it went, or rewrite it for its replacement feature.