refactor: align codebase with EventCrew domain and trim legacy band stack

- Update API: events, users, policies, routes, resources, migrations
- Remove deprecated models/resources (customers, setlists, invitations, etc.)
- Refresh admin app and docs; remove apps/band

Made-with: Cursor

api/app/Models/UserInvitation.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Concerns\HasUlids;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+final class UserInvitation extends Model
+{
+    use HasFactory;
+    use HasUlids;
+
+    protected $fillable = [
+        'email',
+        'invited_by_user_id',
+        'organisation_id',
+        'event_id',
+        'role',
+        'token',
+        'status',
+        'expires_at',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'expires_at' => 'datetime',
+        ];
+    }
+
+    public function invitedBy(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'invited_by_user_id');
+    }
+
+    public function organisation(): BelongsTo
+    {
+        return $this->belongsTo(Organisation::class);
+    }
+
+    public function event(): BelongsTo
+    {
+        return $this->belongsTo(Event::class);
+    }
+}