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/app/Channels/ChannelRegistry.php

@@ -5,7 +5,7 @@ namespace App\Channels;
 use App\Enums\ChannelType;
 use Illuminate\Contracts\Container\Container;
 
-final class ChannelRegistry
+class ChannelRegistry
 {
     public function __construct(private readonly Container $container) {}