fix(deals): keep hot deals within the venue opening hours

[savikthk]

Closes #68

Summary

A hot deal can no longer run past the venue closing. The rule lives in the service, so the bot, the mini app and the HTTP API agree: POST and PATCH /api/v1/venue/deals answer 422 deal_ends_after_closing when endsAt is later than the nearest closing or the venue is closed now (rejected rather than cut, so the client knows the term was not accepted). A scheduled deal is checked against the closing after its start. Round the clock venues have no closing limit and hours past midnight work.

The wizard in the bot and the mini app offer "1 час" and "2 часа" only when they end before the closing, just "До закрытия, ЧЧ:ММ" in the last hour, and less than 15 minutes before the closing or while the venue is closed explain when a deal can be published instead of starting.

Changes

• backend/src/services/deals.ts: assertBeforeClosing in create and update, using nextClosingAt and isOpenAt.
• backend/src/http/routes/venue.ts, backend/src/http/schemas/deals.ts, openapi.yaml: deal_ends_after_closing documented for createDeal and updateDeal.
• backend/src/bot/venue/deals.ts, texts.ts: sale window, fitting durations, paused screen, recovery on deal_ends_after_closing; the old closed venue warning is gone.
• frontend/src/features/venue/dealModel.ts, DealScreens.tsx, frontend/src/api/messages.ts: the same window for creating and changing a deal, including "Другое время".
• docs/scenario.md: step C7.

Testing

• Tests added or updated for the change: service (closing, before opening, after closing, PATCH, scheduled deal, past midnight, round the clock), routes, bot, mini app.
• npm run lint, npm run typecheck and npm test pass locally (backend and frontend), npm run build passes.
• Manual, local API with demo data at 23:16 MSK: creating a deal in the closed «Зерно» answered 422 deal_ends_after_closing.
• Tests changed on purpose:
  • does not offer closing time when the venue %s: the closes in ten minutes case pinned the defect and is rewritten; the round the clock case still offers 1 and 2 hours.
  • warns that guests cannot book while the venue is closed: deals can no longer be published while the venue is closed, including before opening.
  • needs an end in the future and within 24 hours: the accepted 24 hour deal moved to a round the clock venue.
  • Mini app disables discounts ... warns about a closed venue: now expects the explanation and a disabled "Опубликовать".