Add AutoInterface: IPv6 multicast peer discovery for Python RNS interop

[Pmmlabs]

Implements automatic peer discovery via IPv6 multicast matching Python RNS AutoInterface protocol. Features:

• Multicast address derived from group_id hash (default: "reticulum")
• Discovery token verification using full SHA-256 hash
• Peer management with expiration and duplicate detection
• Discovery-only mode when data port unavailable

Verified interoperability: successfully discovers peers from Python RNS AutoInterface on the same network segment (Wi-Fi).
I also tested it with RNode - LXMF messages from Wi-Fi are routed to LoRa interface and delivered to RNode. And vice-versa.

I've taken this implementation from microReticulum fork by tolando-tech and corrected a bit.

[angel523323]

I have tested this and can attest that it is working on my Heltec V3 as a transport node between LoRa and Wifi(AutoInterface). Configuration for connecting in the wifi is the same as normal rnodes with rnodeconf, handy!

Announce Propagation works.
Direct Packets work.
Links do not work. (Unsure if this is implemented yet, and if it works for LoRa <-> LoRa transport in upstream)