Split bills + kitchen ingest for online orders

Split bills (restaurant tickets):
- New pos_payments ledger; a tab is settled across one or more cash/Ladill Pay
  payments. The ticket shows total / paid / balance, an amount field with Full /
  ½ / ⅓ / ¼ helpers, and the payments taken. Partial payments keep the tab open;
  the sale finalises (and frees the table) only when the balance hits zero.
  Pay splits get their own checkout + callback (pos.payments.callback).

Pipe online orders to the KDS:
- POST /api/kitchen/orders — a first-party, service-keyed ingest
  (config pos.kitchen_api_keys, scoped by owner, idempotent by external_ref) that
  creates a paid, already-fired ticket (order_type=online, lines source=online).
- The KDS feed is now payment-agnostic (any kitchen-active sale), so paid online
  orders sit on the board next to dine-in tabs and bump the same way; they're
  badged "online".

Schema additive: pos_payments, pos_sales.external_ref. Suite green (14).

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

database/migrations/2026_06_30_000000_create_pos_payments.php

@@ -0,0 +1,29 @@
+<?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_payments', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('pos_sale_id')->constrained('pos_sales')->cascadeOnDelete();
+            $table->string('owner_ref')->index();
+            $table->unsignedInteger('amount_minor');
+            $table->string('method')->default('cash'); // cash | pay
+            $table->string('status')->default('pending'); // pending | paid | failed
+            $table->unsignedBigInteger('pay_order_id')->nullable();
+            $table->string('payment_reference')->nullable()->index();
+            $table->timestamp('paid_at')->nullable();
+            $table->timestamps();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('pos_payments');
+    }
+};

database/migrations/2026_07_01_000000_add_external_ref_to_pos_sales.php

@@ -0,0 +1,23 @@
+<?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::table('pos_sales', function (Blueprint $table) {
+            // Source order id for ingested online orders (e.g. a Merchant order) — for idempotency.
+            $table->string('external_ref')->nullable()->after('reference')->index();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('pos_sales', function (Blueprint $table) {
+            $table->dropColumn('external_ref');
+        });
+    }
+};