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/platega.py

@@ -609,6 +609,7 @@ async def _create_webapp_payment(ctx: WebAppPaymentContext, variant: str) -> web
             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,