backend: align API/models with current PostgreSQL schema

app/Models/Offer.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+
+class Offer extends Model
+{
+    use HasFactory;
+
+    public $timestamps = false;
+
+    protected $fillable = [
+        'venue_id',
+        'title',
+        'description',
+        'image_url',
+        'start_at',
+        'end_at',
+        'is_active',
+        'created_at',
+    ];
+
+    protected $casts = [
+        'is_active' => 'boolean',
+        'start_at' => 'datetime',
+        'end_at' => 'datetime',
+    ];
+}