ADR-104 Part B: first-run claim protocol (console-token-gated, self-locking)

[aaronsb]

Implements Part B of ADR-104: a console-token-gated, self-locking first-run claim protocol so the platform boots UNCLAIMED and identity bootstrap moves out of the install scripts into the API.

Threat model: closes the WordPress install.php takeover window (token originates off-network, console/installer-only); pfSense-style console-sourced secret.

• API: UNCLAIMED/CLAIMED state; "admin exists" ⇒ CLAIMED (existing installs unaffected).
• API: GET /setup/status, POST /setup/claim (single-use token, creates admin + stores provider key, burns token, → CLAIMED; /setup/* → 410 after).
• init paths mint the token instead of pre-creating an admin; surface on console (kg-console.sh), install.sh stdout, root file.
• Web /setup page gated on unclaimed state.
• cloud-init provision.env boots pre-CLAIMED (declarative path).
• Recovery: configure.py reset-claim (re-open setup).
• Remove admin/provider bootstrap from install.sh / headless-init.sh / kg-firstboot.sh.

Security-sensitive; relates ADR-400/074/054. Refs ADR-104.