Add Frontdesk-style Devices registry for POS hardware.

Register tills, customer displays, kitchen screens, printers, scanners,
and tablets per branch. Customer displays share the branch display token
and mark online when the public screen polls; stale devices go offline
on a schedule.

database/migrations/2026_07_15_220000_create_pos_devices_table.php

@@ -0,0 +1,31 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('pos_devices', function (Blueprint $table) {
+            $table->id();
+            $table->string('owner_ref', 64)->index();
+            $table->foreignId('location_id')->nullable()->constrained('pos_locations')->nullOnDelete();
+            $table->string('name');
+            $table->string('type', 40)->index();
+            $table->string('status', 20)->default('offline')->index();
+            $table->string('device_token', 64)->nullable()->unique();
+            $table->json('config')->nullable();
+            $table->timestamp('last_online_at')->nullable();
+            $table->timestamps();
+
+            $table->index(['owner_ref', 'type']);
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('pos_devices');
+    }
+};