add timescaledb extension migration and orders_daily_by_created continuous aggregate

P22.1 of Stage 22 materialization layer infrastructure. Adds explicit
CREATE EXTENSION migration so clean environments can run `migrate` end-to-end
without ops manual setup, then creates the first continuous aggregate
orders_daily_by_created (day-bucketed, grouped by company/platform/store)
with WITH NO DATA. Five composite indexes cover the high-frequency query
patterns documented in docs/data_query.md. P22.2/P22.3 will add the
by-paid view, refresh policy and historical backfill on top.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/migrations/2026_05_07_100000_enable_timescaledb_extension.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+use Hyperf\DbConnection\Db;
+use Hyperf\Database\Migrations\Migration;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Db::statement('CREATE EXTENSION IF NOT EXISTS timescaledb');
+    }
+
+    public function down(): void
+    {
+        // 不主动 DROP EXTENSION：existing hypertables 依赖该扩展，drop 会破坏数据。
+        // 完全清空数据库时手动执行 `DROP EXTENSION timescaledb CASCADE`。
+    }
+};