Feature Request: ESP-NOW Message Bridge for MeshCore (ESP32-only)

[themelisx]

Summary
Add an optional bidirectional ESP-NOW message bridge to MeshCore, allowing ESP32-based nodes to forward messages between MeshCore and ESP-NOW devices (sensors, displays, peripherals).

Functionality

MeshCore → ESP-NOW
When a MeshCore client receives a message (public, channel, or private), it can optionally rebroadcast it via ESP-NOW.

• ESP32-only
• Disabled by default
• Enabled via UI
• No behavior change when disabled

ESP-NOW → MeshCore
ESP32 devices using ESP-NOW can send messages into MeshCore.

• Messages are received by an ESP32 MeshCore node
• Validated and injected into MeshCore routing
• Routed as public, channel, or private messages

Sensor / Display Use Case
This feature can also support data transport between ESP32-based sensors and display devices:

• Sensor nodes send readings via ESP-NOW
• A MeshCore ESP32 node acts as a bridge
• Data is forwarded to Heltec or Elecrow displays

This enables lightweight sensor nodes without running the full MeshCore stack.

Configuration / Constraints

• ESP-NOW available only on ESP32
• Feature hidden or disabled on other MCUs
• UI toggle: Enable ESP-NOW Message Bridge (default: off)
• Optional direction toggles (inbound / outbound)

Proposed Sub-Tasks

• ESP32 platform detection & ESP-NOW init
• Define lightweight ESP-NOW message format
• MeshCore → ESP-NOW rebroadcast hook
• ESP-NOW → MeshCore message injection
• UI toggles (global + direction)
• Loop prevention & basic validation

Motivation
Turns MeshCore into a gateway for ESP-NOW peripherals, enabling sensor-to-display data flow and local ESP32 device integration.