feat(access): access-control gate — npub-QR badge + PIN + dev bypass (ADR-003)

Squashed skeleton (was 11 commits on feat/access-control-skeleton) for a
clean rebase onto dev. Adds a `locked` gate the terminal boots into until a
credential is presented; opt-in and non-breaking (defaults off → boots
straight to idle as before).

- state-machine: `locked` state + ACCESS_GRANTED/ACCESS_DENIED/DEV_UNLOCK
  events + accessBypass/devUnlockAllowed guards (packages/state-machine).
- services/access: reader abstraction, npub+PIN authorize() (nostr-tools
  nip19; accepts nostr:/nprofile), camera npub-QR reader, mock reader.
- LockedView.vue + ColorModeToggle: branded viewfinder, PIN pad, denied
  reason, dev-unlock; camera off-by-default + idle return.
- store/main/electron.d.ts: seed gate config, grant/deny/devUnlock wiring,
  access.json provisioning (no rebuild), get-config surface.
- deploy: access.example.json + provision-access.sh; ADR-003.

Credential union is npub today; UID (NFC tap) is the next step.

deploy/nixos/access.example.json

@@ -0,0 +1,5 @@
+{
+  "enabled": true,
+  "openEnrollment": true,
+  "devUnlock": true
+}

deploy/nixos/provision-access.sh

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+# Provision the access-control gate (ADR-003) to a deployed bitSpire ATM.
+# Pushes an access.json to /var/lib/bitspire/ and restarts the service, so the
+# gate can be toggled on a machine without an image rebuild (mirrors
+# provision-branding.sh). Env defaults are overridden by whatever this file sets.
+#
+# Usage:
+#   bash provision-access.sh <access.json>                    # SSH to localhost:2222 (QEMU)
+#   bash provision-access.sh <access.json> 192.168.1.50       # a real ATM on the LAN
+#   bash provision-access.sh <access.json> 192.168.1.50 22    # custom SSH port
+#
+# access.json schema (all keys optional; omitted keys fall back to env/defaults):
+#   {
+#     "enabled": true,           // master switch for the gate
+#     "openEnrollment": true,    // prototype: admit any valid npub
+#     "devUnlock": true,         // allow the on-screen dev/operator unlock
+#     "salt": "per-machine",     // hashing salt (provision a real one for prod)
+#     "allowList": [             // authorized identities (hashed); empty in open mode
+#       { "idHash": "<hashId(hexpubkey,salt)>", "role": "user", "pinHash": "<hashPin(pin,salt)>" }
+#     ]
+#   }
+#
+# To DISABLE the gate again: push a file with {"enabled": false} (or delete
+# /var/lib/bitspire/access.json on the machine) and restart.
+set -euo pipefail
+
+ACCESS_FILE="${1:-}"
+ATM_HOST="${2:-localhost}"
+ATM_SSH_PORT="${3:-2222}"
+ATM_USER="bitspire"
+REMOTE_FILE="/var/lib/bitspire/access.json"
+
+if [ -z "$ACCESS_FILE" ]; then
+    echo "Usage: $0 <access.json> [host] [port]" >&2
+    echo "       $0 ./access.json                       (QEMU on localhost:2222)" >&2
+    echo "       $0 ./access.json 192.168.1.50          (real ATM)" >&2
+    exit 1
+fi
+
+if [ ! -f "$ACCESS_FILE" ]; then
+    echo "ERROR: access file not found: $ACCESS_FILE" >&2
+    exit 1
+fi
+
+# Fail fast on malformed JSON before touching the machine.
+if command -v jq >/dev/null 2>&1; then
+    jq empty "$ACCESS_FILE" || { echo "ERROR: $ACCESS_FILE is not valid JSON" >&2; exit 1; }
+fi
+
+echo "=== Provisioning access gate to $ATM_HOST:$ATM_SSH_PORT ==="
+echo "Local file : $ACCESS_FILE"
+echo "Remote file: $REMOTE_FILE"
+cat "$ACCESS_FILE"
+echo ""
+
+# Copy over SSH. --rsync-path=sudo because /var/lib/bitspire is owned by the
+# bitspire service user, not the SSH user.
+rsync -avz \
+    --rsync-path="sudo rsync" \
+    -e "ssh -o StrictHostKeyChecking=no -p $ATM_SSH_PORT" \
+    "$ACCESS_FILE" \
+    "$ATM_USER@$ATM_HOST:$REMOTE_FILE"
+
+# Restart so loadAccessControl() re-reads the file.
+ssh -o StrictHostKeyChecking=no -p "$ATM_SSH_PORT" "$ATM_USER@$ATM_HOST" \
+    "sudo systemctl restart bitspire"
+
+echo ""
+echo "=== Access gate provisioned. Service restarted. ==="