Multi-mode Schedule tab UX for days/stages reveal levels

[chiptus]

Goal

Render the Schedule tab progressively at lower reveal levels, instead of the placeholder.

Behavior per level

• draft — current "Schedule not yet published" placeholder (unchanged).
• days — day-grouped lineup view (Friday / Saturday / Sunday → list of artists/sets per day). No stage, no times.
• stages — stage × day grid. Each cell lists artists/sets on that stage that day. No times.
• full — current Timeline / List views (unchanged).

Notes

• The progressive Artist-tab SetCard reveal (set time + stage badge) ships with the parent issue and is independent of this.
• Filtering/sorting controls on the Schedule tab need to follow the level: at days you can only filter by day; at stages by day + stage; at full everything including time-of-day.
• Both Timeline and List tabs need a defined "non-full" rendering, or we collapse them into a single view for sub-full levels.

Blocked by

#46 — depends on the schedule_reveal_level enum + column-masking infrastructure landing first.