[2.8.0] Align licensed remote Admin transport and signature UI

[RCGV1]

Description

Align Apple remote administration with the signed plaintext licensed-mode design in meshtastic/design#123 and meshtastic/firmware#10972.

Apple currently emits Admin packets without setting PKI fields. Preserve that licensed plaintext behavior explicitly, test it across Admin call paths, and update remote-Admin wording so licensed mode does not claim PKI encryption. Normal-mode wording and transport behavior must remain unchanged.

Scope

• Add a central outbound invariant for remote ADMIN_APP through a licensed connected radio: channel 0, pkiEncrypted=false, and empty packet public key.
• Determine mode from the connected local UserEntity.isLicensed, not the destination callsign/licensed bit.
• Cover Admin requests/mutations that use the shared helper and any direct sends that bypass it.
• Update licensed-mode picker/request wording from “PKI Admin” to signed plaintext/verified Admin while retaining PKI wording in normal mode.
• Keep shield/lock semantics accurate: signature shield for verified licensed Admin, never an encryption lock.
• Avoid a broad refactor of individual request/save functions; prefer one policy hook.

Acceptance criteria

• Every licensed local → remote Admin getter, session request, and mutation has plaintext packet fields.
• Normal-mode remote Admin behavior and wording remain unchanged.
• Self/local Admin behavior remains unchanged.
• Unknown local owner state does not assume licensed mode.
• Tests record outgoing packets for licensed, normal, self, and unknown-mode cases and cover conditional UI wording.
• PR remains draft until paired two-radio validation with firmware#10972 proves readable plaintext signed Admin request/reply behavior.

Dependencies

• Design: [FOLLOW-UP] [ALIGNMENT]: Signed plaintext remote administration in licensed mode design#123
• Firmware: Authorize signed plaintext remote admin in licensed mode firmware#10972
• Licensed signing: Sign plaintext packets in licensed mode firmware#10969