fix(config): point batm3 validator at /dev/ttyMEI (was nonexistent ttyACM0)

The batm3 preset defaulted the EBDS validator to /dev/ttyACM0, assuming a
CDC-ACM BNR Advance. The actual MEI acceptor enumerates as a USB-serial
device (ttyUSB*), exposed via the stable udev symlink /dev/ttyMEI
(batm3.nix). Because /dev/ttyACM0 never existed, hal-service skipped the
validator entirely and logged "[HAL] No validator — cash-in disabled", so
Buy Bitcoin silently ignored inserted bills.

Verified on hardware: with the correct device the validator starts, and
(with the EBDS latch fix) a bill escrows → stacks → credits. Removes the
need for the VITE_LAMASSU_VALIDATOR_DEVICE=/dev/ttyMEI per-box override.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/machine/src/config/device.ts

@@ -139,7 +139,12 @@ export const MACHINE_PRESETS: Record<MachineModel, Omit<DeviceConfig, 'fiatCode'
     model: 'batm3',
     validator: {
       type: 'ebds',
-      device: '/dev/ttyACM0',
+      // MEI bill acceptor (EBDS) on a USB-serial bridge, exposed via the
+      // stable udev symlink /dev/ttyMEI (batm3.nix, serial A9YW78OC). The old
+      // /dev/ttyACM0 default assumed a CDC-ACM BNR; this hardware enumerates as
+      // ttyUSB* instead, so ACM0 never existed and cash-in was silently
+      // disabled ("[HAL] No validator"). Per-box override: VITE_LAMASSU_VALIDATOR_DEVICE.
+      device: '/dev/ttyMEI',
     },
     dispenser: {
       type: 'f56',