Refactor: Enforce type safety, fix close deadlock, implement assignee restrictions and notify admin fallbacks

app/Models/User.php

@@ -7,6 +7,7 @@ use Illuminate\Database\Eloquent\Attributes\Fillable;
 use Illuminate\Database\Eloquent\Attributes\Hidden;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Foundation\Auth\User as Authenticatable;
 use Illuminate\Notifications\Notifiable;
 use Spatie\Permission\Traits\HasRoles;
@@ -14,7 +15,7 @@ use Illuminate\Contracts\Auth\Access\Authorizable;
 use Filament\Models\Contracts\FilamentUser;
 use Filament\Panel;
 
-#[Fillable(['name', 'email', 'password', 'role'])]
+#[Fillable(['name', 'email', 'password', 'role', 'department_id'])]
 #[Hidden(['password', 'remember_token'])]
 class User extends Authenticatable implements FilamentUser
 {
@@ -29,6 +30,11 @@ class User extends Authenticatable implements FilamentUser
         ];
     }
 
+    public function department(): BelongsTo
+    {
+        return $this->belongsTo(Department::class);
+    }
+
     public function canAccessPanel(Panel $panel): bool
     {
         return true;