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/wata.py

@@ -978,6 +978,7 @@ 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,
     )
     months_for_lookup = (
         reuse_amounts.months if sale_mode_base(ctx.sale_mode) == "subscription" else None