feat(appointment): log cancellation events and show them in a Timeline

Introduce the first per-appointment event system. On cancel (via the status
or general update endpoints) an AppointmentEvent (type=cancelled, «نوبت لغو
شد») is recorded with the actor, cancel time, and an optional cancel_reason,
plus a warning-level app_log entry. New GET /appointment/{uuid}/events
returns the ordered event list. The admin appointment detail page renders a
Timeline section and the cancel dialog now collects an optional reason.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Appointment/Entity/AppointmentEvent.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace App\Appointment\Entity;
+
+use App\Appointment\Repository\AppointmentEventRepository;
+use Doctrine\ORM\Mapping as ORM;
+use Symfony\Component\Uid\Uuid;
+
+/**
+ * تاریخچه‌ی رویدادهای یک نوبت (Timeline). فعلاً فقط رویداد لغو ثبت می‌شود، اما
+ * ساختار عمومی است تا رویدادهای بعدی (ایجاد/تأیید/جابه‌جایی) هم قابل افزودن باشند.
+ */
+#[ORM\Entity(repositoryClass: AppointmentEventRepository::class)]
+#[ORM\Table(name: 'appointment_events')]
+#[ORM\Index(columns: ['appointment_id', 'created_at'], name: 'idx_appointment_events_appt')]
+class AppointmentEvent
+{
+    public const TYPE_CANCELLED = 'cancelled';
+
+    #[ORM\Id]
+    #[ORM\GeneratedValue]
+    #[ORM\Column(type: 'integer')]
+    private ?int $id = null;
+
+    #[ORM\Column(type: 'string', length: 36, unique: true)]
+    private string $uuid;
+
+    #[ORM\ManyToOne(targetEntity: Appointment::class)]
+    #[ORM\JoinColumn(name: 'appointment_id', nullable: false, onDelete: 'CASCADE')]
+    private Appointment $appointment;
+
+    #[ORM\Column(type: 'string', length: 40)]
+    private string $type;
+
+    #[ORM\Column(type: 'string', length: 191)]
+    private string $title;
+
+    // کاربرِ عاملِ رویداد (مثلاً لغوکننده)؛ null برای رویدادهای سیستمی.
+    #[ORM\Column(name: 'actor_user_id', type: 'integer', nullable: true)]
+    private ?int $actorUserId = null;
+
+    // کشِ نام عامل برای نمایش بدون join اضافه.
+    #[ORM\Column(name: 'actor_name', type: 'string', length: 191, nullable: true)]
+    private ?string $actorName = null;
+
+    #[ORM\Column(type: 'text', nullable: true)]
+    private ?string $reason = null;
+
+    #[ORM\Column(name: 'created_at', type: 'integer')]
+    private int $createdAt;
+
+    public function __construct(Appointment $appointment, string $type, string $title)
+    {
+        $this->uuid        = Uuid::v4()->toRfc4122();
+        $this->appointment = $appointment;
+        $this->type        = $type;
+        $this->title       = $title;
+        $this->createdAt   = time();
+    }
+
+    public function setActor(?int $userId, ?string $name): self { $this->actorUserId = $userId; $this->actorName = $name; return $this; }
+    public function setReason(?string $reason): self { $this->reason = $reason; return $this; }
+
+    public function getUuid(): string { return $this->uuid; }
+
+    public function toArray(): array
+    {
+        return [
+            'uuid'       => $this->uuid,
+            'type'       => $this->type,
+            'title'      => $this->title,
+            'actor_name' => $this->actorName,
+            'reason'     => $this->reason,
+            'created_at' => $this->createdAt,
+        ];
+    }
+}