Support iroh for P2P remote access

I'd like to propose adding optional support for [**iroh**](https://www.iroh.computer/) as a remote transport for the Home Assistant Companion App.

The idea is to allow direct, end-to-end encrypted peer-to-peer connections between the Companion App and Home Assistant using iroh's persistent peer identities, automatic NAT traversal (hole punching), and relay fallback when needed.

This could provide secure remote access without port forwarding, a VPN, or a reverse proxy, while offering a more seamless, app-native experience than solutions like Tailscale.

From a user's perspective, setup could be as simple as pairing once (e.g. via QR code), after which the app would use the local network when available and automatically fall back to iroh when away from home.

I'd be interested to hear whether this is something the project would consider architecturally.

The issue names no files, tests, or entry points. Begin by reviewing the Android Companion App's existing remote-access and pairing architecture, then determine whether iroh can support the proposed local-network fallback, peer pairing, NAT traversal, encryption, and relay behavior; done would require an agreed architectural direction.

Written by the indexing model from the issue text.