List the events affecting each night #97

Problem

The events endpoint lists events by date range, but the calendar and night detail need them per night, with details the manager understands: a three-day festival should show on each of its nights as "day 1 of 3", "day 2 of 3" and so on.

Goal

For any night, the API returns the events affecting it, ready to show to the manager.

Scope

• A service that, for a range of nights, returns each night's events: name, venue, category, expected attendance, and day N of M for multi-day events.
• Sort each night's events by how much they matter (e.g. attendance or rank), biggest first.
• Used by the recommendations range route (event names only) and the night detail endpoint (full details).
• Hide withdrawn events, as the events endpoint already does.

Considerations

• Use the same rule for which events affect a night as the model does, so what the manager sees matches what drives the rate.
• Events with no venue or attendance should still show, with those fields empty.

Acceptance criteria

• A multi-day event appears on each of its nights with the right "day N of M".
• Withdrawn events don't appear.
• Tests cover single-day, multi-day and overlapping events.