feat: save ai usage

database/migrations/2026_05_24_084353_create_ai_usages_table.php

@@ -0,0 +1,44 @@
+<?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('ai_usages', function (Blueprint $table) {
+            $table->ulid('id')->primary();
+            $table->foreignUlid('user_id')->nullable()->constrained('users')->nullOnDelete();
+            $table->string('type', 64);
+            $table->string('status', 32);
+            $table->json('input')->nullable();
+            $table->json('output')->nullable();
+            $table->string('provider')->nullable();
+            $table->string('model')->nullable();
+            $table->unsignedInteger('prompt_tokens')->nullable();
+            $table->unsignedInteger('completion_tokens')->nullable();
+            $table->unsignedInteger('total_tokens')->nullable();
+            $table->text('error_message')->nullable();
+            $table->string('related_type')->nullable();
+            $table->string('related_id', 36)->nullable();
+            $table->timestamps();
+
+            $table->index(['user_id', 'type', 'created_at']);
+            $table->index(['type', 'status', 'created_at']);
+            $table->index(['related_type', 'related_id']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('ai_usages');
+    }
+};