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

tests/test_payments.py

@@ -287,7 +287,7 @@ class SubscribeCommandTests(unittest.IsolatedAsyncioTestCase):
         with (
             patch.object(bot, "DEPLOY_ENV", "development"),
             patch.dict(os.environ, {"BOT_DB_PATH": db}),
-            patch.object(bot.asyncio, "to_thread", new=AsyncMock(return_value=32)) as to_thread,
+            patch.object(bot.asyncio, "to_thread", new=_direct_thread_mock()) as to_thread,
         ):
             await bot.confirm_development_payment(callback)
         db_row = user_store.subscription_row(42, db)