Graywolf RXT test build acaaa358

Fixes CA2RXU signed commands for tactical iGates and preserves the signed identity during partial API updates.

Upgrade and restart Graywolf, then refresh the browser. In Key settings, set RF recipient to the on-air name and signed identity to the iGate's Station Callsign-SSID. Leave the secret blank to preserve the key and counter. Verify the destination conversation's RF route and channel. No firmware update is needed.

API updates: omitted or null signed_target keeps the saved identity; an explicit empty string defaults to the RF recipient. Only secret replacement resets the counter. Existing credentials migrate without changing keys or counters. The radio format is unchanged.

Protocol, migration, API, browser and web tests passed. EcoMode was confirmed on the operator's tactical iGate; other devices require RF validation.

Documentation: English walkthrough, French walkthrough, with PDFs in the handbook.

Commit: acaaa35. Base version: 0.14.14. RXT pre-release for testing. No OCI images; GHCR latest unchanged.