fix(subscription): show expiry clock time (MSK) when under a day

- subscription_time_left: replace floor-div '23 ч.'/'мин.' branches with the
  concrete expiry timestamp when less than a full day remains
- add MSK_TIMEZONE (UTC+3) as display default; label time as '(МСК)'
- add shared subscription_status_text helper, use it in status menu,
  post-payment reply and dev confirmation instead of floor-rounded days
- tests: cover under-a-day clock format; fix stale to_thread mock

payments.py

@@ -23,6 +23,8 @@ from user_store import (
     activate_subscription,
     connect,
     ensure_subscription,
+    subscription_row,
+    subscription_status_text,
 )
 
 logger = logging.getLogger(__name__)
@@ -155,7 +157,8 @@ async def handle_successful_payment(message: Message) -> None:
         days = 1
 
     await asyncio.to_thread(ensure_subscription, message.from_user.id)
-    days_left = await asyncio.to_thread(activate_subscription_days, message.from_user.id, days)
+    await asyncio.to_thread(activate_subscription_days, message.from_user.id, days)
+    sub = await asyncio.to_thread(subscription_row, message.from_user.id, db_path)
     await asyncio.to_thread(
         save_payment,
         charge_id,
@@ -165,9 +168,7 @@ async def handle_successful_payment(message: Message) -> None:
         payment.total_amount,
         db_path,
     )
-    await message.answer(
-        f"Подписка активна\nЗакончится через {days_left} дн."
-    )
+    await message.answer(subscription_status_text(sub))
 
 
 async def _reject(message: Message, charge_id: str, reason: str) -> None: