feat: Implement Slack, Trello, and Courier (ShipLogic) integration

- Add 14 domain events for order lifecycle (OrderCreated, OrderPacked, ShipmentCreated, ParcelDelivered, etc.)
- Create SlackNotifierService with channels for orders, design, production, shipping, ops-alerts
- Create TrelloService to create cards, move cards between lists, attach files, check items
- Create CourierService to integrate with ShipLogic API for shipment creation and document retrieval
- Create PackingController to explicitly capture packing dimensions and weight
- Create ShippingController with multi-layer guards: packing validation, payment/approval verification, idempotency
- Create TrelloWebhookController to handle incoming Trello webhooks as intent signals
- Create CourierWebhookController to handle Shiplogic status updates
- Create event listeners for Slack notifications and Trello card updates
- Create EventServiceProvider to register all events and listeners
- Add database migration for packing, courier, and Trello data columns
- Create config files for slack, trello, and courier integration
- Update .env with integration secrets placeholders
- Add routes for /orders/{id}/pack, /orders/{id}/ship, /api/webhooks/trello, /api/webhooks/courier

Key architectural decisions:
- Packing is explicit ops action (not automatic from status)
- Shipment creation only after: Trello intent + packing confirmed + payment/approval rules met
- Courier API failures keep order in Ready to Ship state (safe retry)
- Trello and Slack are mirrors of backend state, not decision makers
- All side effects flow through event listeners, maintaining separation of concerns

app/Providers/EventServiceProvider.php

@@ -0,0 +1,98 @@
+<?php
+
+namespace App\Providers;
+
+use App\Events\BalancePaid;
+use App\Events\DepositPaid;
+use App\Events\OrderCreated;
+use App\Events\OrderPacked;
+use App\Events\ParcelCollected;
+use App\Events\ParcelDelivered;
+use App\Events\ParcelFailedDelivery;
+use App\Events\ParcelInTransit;
+use App\Events\ProofApproved;
+use App\Events\ProofRevisionRequested;
+use App\Events\ProofUploaded;
+use App\Events\ShipmentCreated;
+use App\Events\ShipmentCreationFailed;
+use App\Listeners\NotifySlackOnOrderCreated;
+use App\Listeners\NotifySlackOnOrderPacked;
+use App\Listeners\NotifySlackOnParcelCollected;
+use App\Listeners\NotifySlackOnParcelDelivered;
+use App\Listeners\NotifySlackOnParcelFailedDelivery;
+use App\Listeners\NotifySlackOnShipmentCreated;
+use App\Listeners\NotifySlackOnShipmentCreationFailed;
+use Illuminate\Auth\Events\Registered;
+use Illuminate\Auth\Listeners\SendEmailVerificationNotification;
+use Illuminate\Foundation\Support\Providers\EventServiceProvider as ServiceProvider;
+
+class EventServiceProvider extends ServiceProvider
+{
+    /**
+     * The event to listener mappings for the application.
+     *
+     * @var array<class-string, array<int, class-string>>
+     */
+    protected $listen = [
+        // Order events
+        OrderCreated::class => [
+            NotifySlackOnOrderCreated::class,
+        ],
+
+        // Packing events
+        OrderPacked::class => [
+            NotifySlackOnOrderPacked::class,
+        ],
+
+        // Shipment events
+        ShipmentCreated::class => [
+            NotifySlackOnShipmentCreated::class,
+        ],
+        ShipmentCreationFailed::class => [
+            NotifySlackOnShipmentCreationFailed::class,
+        ],
+
+        // Courier events
+        ParcelCollected::class => [
+            NotifySlackOnParcelCollected::class,
+        ],
+        ParcelInTransit::class => [
+            // TODO: Add listener
+        ],
+        ParcelDelivered::class => [
+            NotifySlackOnParcelDelivered::class,
+        ],
+        ParcelFailedDelivery::class => [
+            NotifySlackOnParcelFailedDelivery::class,
+        ],
+
+        // Custom order events (listeners TODO)
+        DepositPaid::class => [
+            // TODO: NotifySlackOnDepositPaid
+        ],
+        ProofUploaded::class => [
+            // TODO: NotifySlackOnProofUploaded
+        ],
+        ProofApproved::class => [
+            // TODO: NotifySlackOnProofApproved
+        ],
+        ProofRevisionRequested::class => [
+            // TODO: NotifySlackOnProofRevisionRequested
+        ],
+        BalancePaid::class => [
+            // TODO: NotifySlackOnBalancePaid
+        ],
+
+        Registered::class => [
+            SendEmailVerificationNotification::class,
+        ],
+    ];
+
+    /**
+     * Register any events for your application.
+     */
+    public function boot(): void
+    {
+        //
+    }
+}