feat: add ColumnComment model and migration for tracking field-level comments

database/migrations/2026_04_28_230000_create_column_comments_table.php

@@ -0,0 +1,39 @@
+<?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
+    {
+        if (!Schema::hasTable('column_comments')) {
+            Schema::create('column_comments', function (Blueprint $table) {
+                $table->id();
+                $table->string('table_name');
+                $table->unsignedBigInteger('record_id');
+                $table->string('column_name');
+                $table->text('comment');
+                $table->text('column_value')->nullable();
+                $table->unsignedBigInteger('user_id')->nullable();
+                $table->string('ip_address', 45)->nullable();
+                $table->timestamps();
+
+                $table->index(['table_name', 'record_id']);
+                $table->index(['table_name', 'column_name']);
+            });
+        }
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('column_comments');
+    }
+};