feat(C-02)：工具热榜周榜+最近使用

新增ToolUsageRecord使用日志（tool+created_at索引）；/tool/top/总榜按累计排序、周榜按近7天聚合（无日志回退总榜，兼容period旧参）；/tool/recent/登录去重倒序；seed新增AI图片放大/代码运行两个工具。

tool/migrations/0007_alter_colorhistory_id_toolusagerecord.py

@@ -0,0 +1,37 @@
+# Generated by Django 5.2.12 on 2026-09-08 08:24
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('tool', '0006_merge_0005'),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='colorhistory',
+            name='id',
+            field=models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID'),
+        ),
+        migrations.CreateModel(
+            name='ToolUsageRecord',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('session_id', models.CharField(blank=True, default='', max_length=64, verbose_name='会话ID')),
+                ('created_at', models.DateTimeField(auto_now_add=True, verbose_name='使用时间')),
+                ('tool', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='usage_records', to='tool.tool', verbose_name='工具')),
+                ('user', models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='tool_usage_records', to=settings.AUTH_USER_MODEL, verbose_name='用户')),
+            ],
+            options={
+                'verbose_name': '工具使用记录',
+                'verbose_name_plural': '工具使用记录',
+                'ordering': ['-created_at'],
+                'indexes': [models.Index(fields=['tool', 'created_at'], name='tool_toolus_tool_id_4e72d1_idx')],
+            },
+        ),
+    ]