fix: separate HWID device renewal flows

Keep one-off device top-ups scoped to the active subscription term and move device renewal into subscription checkout.

Carry HWID renewal metadata through provider callbacks and webhooks, including YooKassa saved-card flows.

Add admin extension controls, docs, demo data, and regression coverage.

backend/bot/payment_providers/stars.py

@@ -344,6 +344,7 @@ async def create_webapp_payment(ctx: WebAppPaymentContext) -> web.Response:
             months=ctx.months,
             sale_mode=ctx.sale_mode,
             traffic_gb=ctx.traffic_gb,
+            hwid_device_count=ctx.hwid_device_count,
         )
         payment = await create_webapp_payment_record(
             ctx,