Make the LoRa interface IFAC configurable through Provisioning

[jmpuch]

Problem

A microReticulum_Firmware node cannot use an interface access code (IFAC) on its LoRa interface, so it cannot share a LoRa channel with RNS nodes that protect it with network_name / passphrase (Python RNS, RTNode…): its packets carry no code and are dropped, and theirs can't be read.

Solution

Depends on attermann/microReticulum#91 (IFAC support in the library, Interface::setup_ifac()); this PR won't build against a library without it.

• Two fields in the General Provisioning namespace, applied at boot:

  • 8 — "LoRa IFAC Network Name" (FF_REBOOT_REQUIRED)
  • 9 — "LoRa IFAC Passphrase" (FF_REBOOT_REQUIRED | FF_SECRET: persisted, never returned by GET_STATE; deliberately not FF_WRITE_ONLY, which isn't persisted)

  Both empty (default) = IFAC off, so existing nodes are unaffected. Being ordinary Provisioning fields, they also show up in the Console's Transport Config tab.

• rnode_ifac.py (repository root, next to rnodelogs.py): get / set <file.json> / off over USB via CMD_PROVISION_REQ. It reads the passphrase from a JSON file ({"network_name": ..., "passphrase": ...}) rather than the command line, commits, then reboots the node.

• docs/Provisioning.md: new "LoRa interface access code (IFAC)" section.

Testing

• nRF52 hardware — Heltec T114 (built with microReticulum#91), IFAC set with the tool: on a real LoRa link with a node running RTNode-HeltecV4 using the same IFAC, announces propagate and a Link + NomadNet page request from Python RNS instances two and three hops away succeeds. rnode_ifac.py get reads the network name back after reboot.
• Builds of this branch against microReticulum#91: wiscore_rak4631-local (nRF52) and heltec_wifi_lora_32_V4-local (ESP32-S3) succeed. ttgo-lora32-v21-local fails in Pages.h (wifi_mode, udp_interface, wr_device_ip not declared) — the same error happens on unmodified master, unrelated to this change.
• Not tested on ESP32 hardware.

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