feat: tick planner, delivery job, scheduler and purge

Also: test uses disabled channels instead of deleting them (FK cascade); ChannelRegistry no longer final so tests can extend it (controller ruling).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BCrwHHnGCB5XH968Nxokqw

core/tests/Support/FakeRegistry.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Tests\Support;
+
+use App\Channels\ChannelDriver;
+use App\Channels\ChannelRegistry;
+use App\Enums\ChannelType;
+use Illuminate\Container\Container;
+
+final class FakeRegistry extends ChannelRegistry
+{
+    /** @param array<string, ChannelDriver> $drivers keyed by ChannelType value */
+    public function __construct(private readonly array $drivers)
+    {
+        parent::__construct(Container::getInstance());
+    }
+
+    public function for(ChannelType $type): ChannelDriver
+    {
+        return $this->drivers[$type->value];
+    }
+}