feat: Local Mesh Discovery — scan presets for activity

[Yeraze]

Description

Add a Local Mesh Discovery feature similar to the Meshtastic Apple app's scanner. The scanner cycles through LoRa modem presets, listens on each for a configurable period, and reports node count and channel utilization per preset — helping users identify the most active preset in their area.

Use Case

• New node setup: Scan before committing to a preset, find where the local community is active
• Multi-preset awareness: See what's happening on other presets without permanently switching
• Network planning: Understand local spectrum utilization across presets

Implementation Considerations

• The radio goes offline from its normal mesh during a scan — this should be clearly communicated to the user (confirmation dialog, progress indicator)
• Depends on whether the firmware exposes scan/preset-cycling via the serial/TCP protobuf API, or if it's currently Apple-app-only
• Results could be displayed as a ranked table (preset, nodes heard, channel utilization %) with a recommendation
• Could tie into Site Planner or RF Coverage features for a complete "survey your area" workflow

Requested by

NullVoid

Reference

• Apple app docs: https://meshtastic.org/docs/software/apple/user/discovery/

Authored by NodeZero 0️⃣

[Yeraze]

Du