feat: Implement morph maps and historical migration

database/migrations/2026_06_23_091537_update_existing_messages_morph_types.php

@@ -0,0 +1,30 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('messages', function (Blueprint $table) {
+            DB::table('messages')->where('subject_type', 'App\\Models\\User')->update(['subject_type' => 'user']);
+            DB::table('messages')->where('subject_type', 'App\\Models\\Mutation')->update(['subject_type' => 'mutation']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('messages', function (Blueprint $table) {
+            DB::table('messages')->where('subject_type', 'user')->update(['subject_type' => 'App\\Models\\User']);
+            DB::table('messages')->where('subject_type', 'mutation')->update(['subject_type' => 'App\\Models\\Mutation']);
+        });
+    }
+};