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

bot.py

@@ -436,11 +436,14 @@ async def confirm_development_payment(callback: CallbackQuery) -> None:
         await callback.answer("Dev-оплата подтверждена. Срок подписки не изменён.")
         return
     await asyncio.to_thread(ensure_subscription, user_id)
-    days_left = await asyncio.to_thread(user_store.activate_subscription_days, user_id, days)
+    await asyncio.to_thread(user_store.activate_subscription_days, user_id, days)
+    sub = await asyncio.to_thread(subscription_row, user_id)
     await callback.answer("Dev-оплата подтверждена.")
     if isinstance(callback.message, Message):
         await callback.message.edit_reply_markup(reply_markup=None)
-        await callback.message.edit_text(f"Подписка активна\nЗакончится через {days_left} дн.")
+        await callback.message.edit_text(
+            user_store.subscription_status_text(sub)
+        )
 
 
 @router.message(CommandStart())
@@ -470,11 +473,7 @@ async def _show_subscription_info(
     if not sub:
         text = "Подписка закончилась"
     else:
-        active, value, unit = user_store.subscription_time_left(sub)
-        text = (
-            f"Подписка активна\nЗакончится через {value} {unit}"
-            if active else "Подписка закончилась"
-        )
+        text = user_store.subscription_status_text(sub)
 
     if mode == "subscription":
         markup = mode_keyboard("subscription", subscription_purchased=bool(sub and sub["last_paid_at"]))