feat(customers): tambahkan model dan migrasi untuk tabel customers

- Menambahkan model Customer dengan relasi ke akun dan cabang.
- Membuat migrasi untuk tabel customers dengan kolom yang diperlukan.

app/Models/Customer.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Modules\Webstatement\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Modules\Basicdata\Models\Branch;
+
+class Customer extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'customer_code',
+        'name',
+        'address',
+        'branch_code',
+        'date_of_birth',
+        'email',
+    ];
+
+    public function accounts(){
+        return $this->hasMany(Account::class, 'customer_code', 'customer_code');
+    }
+
+    public function branch(){
+        return $this->belongsTo(Branch::class, 'branch_code', 'code');
+    }
+}