refactor(rename): NixOS module + service + paths → bitspire

Five-file coordinated rename to give the dev-branch deploy a clean
`bitspire` namespace at the NixOS level:

  deploy/nixos/lamassu-atm.nix → deploy/nixos/bitspire-atm.nix
    - `services.lamassu-atm`           → `services.bitspire`
    - `systemd.services.lamassu-atm`   → `systemd.services.bitspire`
    - `/var/lib/lamassu-atm`           → `/var/lib/bitspire`
    - `/opt/lamassu-atm`               → `/opt/bitspire`
    - `/etc/lamassu-atm/config.env`    → `/etc/bitspire/config.env`

  flake.nix
    - module import path updated
    - `nixosModules.lamassu-atm` → `nixosModules.bitspire`
    - `system.activationScripts.lamassu-env` → `bitspire-env`
    - all activation-script paths point at /var/lib/bitspire

  deploy/nixos/configuration.nix
    - `networking.hostName = "lamassu-atm"` → `"bitspire"`

  deploy/nixos/live.nix
    - module import path updated
    - ISO name template: `lamassu-atm-<model>-live.iso` → `bitspire-<model>-live.iso`
    - activation-script name updated

  deploy/nixos/provision-atm.sh
    - data-dir paths: /var/lib/lamassu-atm → /var/lib/bitspire
    - systemctl + journalctl unit names updated

DELIBERATELY kept as `lamassu` (for now):
  - The `lamassu` UNIX user and group account. Renaming would
    require file-ownership migration scripts; the Sintra is a
    fresh flash so no existing data, but the internal user
    namespace inconsistency is acceptable.
  - LP-specific bits in provision-atm.sh (admin token, the
    `docker logs lamassu-lightning-pub` extractor) — those
    get ripped out in 3c when the script switches to LNbits.

NO migration activation script added — the Sintra flash is fresh,
production batm3/douro stay on `main` and never see this branch.
A future dev→main cutover will need a separate migration story
(rename UNIX user, move /var/lib/lamassu-atm → /var/lib/bitspire,
SSH key relocation, etc.).

Verified:
  nix eval .#nixosConfigurations.batm3-installed.config.systemd.services.bitspire.enable
    → true
  nix eval .#nixosConfigurations.bitSpire-live-sintra.config.networking.hostName
    → "bitspire"

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

deploy/nixos/configuration.nix

@@ -9,7 +9,7 @@
 
   # Networking
   networking = {
-    hostName = "lamassu-atm";
+    hostName = "bitspire";
 
     # Use NetworkManager for easy WiFi configuration
     networkmanager.enable = true;