feat(user): add changelog read tracking and unread count method

database/migrations/2025_08_07_142403_create_user_changelog_reads_table.php

@@ -0,0 +1,34 @@
+<?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::create('user_changelog_reads', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('user_id')->constrained()->onDelete('cascade');
+            $table->string('changelog_identifier');
+            $table->timestamp('read_at');
+            $table->timestamps();
+
+            $table->unique(['user_id', 'changelog_identifier']);
+            $table->index('user_id');
+            $table->index('changelog_identifier');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('user_changelog_reads');
+    }
+};