feat(01-01): add Member notes relationship, morph map, and NoteFactory

- Add notes() morphMany relationship to Member model (ordered by created_at desc)
- Register morph map in AppServiceProvider ('member' => Member::class)
- Create NoteFactory with forMember() and byAuthor() state methods

app/Models/Member.php

@@ -4,6 +4,7 @@ namespace App\Models;
 
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Support\Facades\Crypt;
 
 class Member extends Model
@@ -110,6 +111,14 @@ class Member extends Model
         return $this->hasMany(Member::class, 'guardian_member_id');
     }
 
+    /**
+     * 會員備註（管理員可對任一會員新增備註）
+     */
+    public function notes(): MorphMany
+    {
+        return $this->morphMany(Note::class, 'notable')->orderBy('created_at', 'desc');
+    }
+
     /**
      * 是否為病友
      */