Add a persisted 12/24-hour time preference to the Explore Set page

[chiptus]

This was generated by AI during triage.

Context

Split off from #174 (reveal-labels module). The Explore Set page's card header currently has no source for a use24Hour preference — unlike SetDetails (URL search param, default true) and the Artists tab (sourced via FestivalSetContext), the Explore route has never had a 12/24-hour toggle at all. #174 unifies this call site onto the shared time-formatting helpers but intentionally passes a fixed default rather than inventing new state, to keep that refactor narrow.

What's needed

Give the Explore page a real, persisted use24Hour preference. Discussed during #174's design: this should not be a URL search param (unlike SetDetails) — prefer localStorage or a user profile/DB setting, so the preference persists across sessions and (ideally) is shared consistently with the other views rather than being re-decided per route.

Relations

• explore: a reveal-labels module — replace the dead maskSetForReveal and four inline triads #174 (reveal-labels module) — this ticket exists because that one deliberately left this out of scope.

Architecture note

Filed during triage grilling of #174 (architecture review batch, 2026-07-13).

[chiptus]

This was generated by AI during triage.

Agent Brief

Category: enhancement
Summary: Add a persisted 12/24-hour time-format preference on the user's profile, surfaced via a toggle in a settings surface, and read it on the Explore Set page.

Current behavior:
The Explore Set page has no source at all for a use24Hour preference. This is one of three inconsistent sources across the app for what's conceptually a single user preference: SetDetails and the Vote tab read it from a URL search param (default true); a separate context used by the Artists tab has its own local default (false) unrelated to any persisted setting. The app already has one precedent for a persisted-per-user preference: active_group_id on the profiles table (added for the in-progress Active Group epic, #122), read via the existing profile query hook.

The group epic (#122) is expected to eventually ship a proper settings surface — a mocked "Settings card" appears in one of the exploratory prototype variants in PR #288 — but as of this brief, #122 is unimplemented and PR #288 is a throwaway, dev-only prototype (mock data, gated out of production builds, not linked from any real navigation). There is currently no real settings surface anywhere in the app.

Desired behavior:

• A new field on the user's profile persists the 12/24-hour preference, following the same migration/read/write shape already established for active_group_id.
• The Explore Set page reads this persisted preference (instead of having no source at all) when formatting times.
• Before building any UI, check whether a real (non-prototype) settings surface already exists in the app — Active Group: app-wide group perspective/scope for votes #122 may have landed by the time this is picked up. If it has, add the toggle there.
• If no real settings surface exists yet, create a minimal one to host just this toggle: a simple, generically-named page (not Explore-specific), reachable from an obvious, real place in the app's navigation (e.g. a profile/account menu) — not a hidden or dev-only route. Keep it deliberately minimal and undecorated rather than fully designed, since Active Group: app-wide group perspective/scope for votes #122's eventual settings view is likely to absorb or replace it — the goal is a working home for this one control, not a finished settings page.
• Changing the toggle updates the Explore Set page's time format immediately, without a page reload.
• A logged-out or no-profile state falls back to the same default the Explore page effectively has today, with no crash or error.

Key interfaces:

• profiles table — new persisted field for the 12/24-hour preference, mirroring the active_group_id column/migration pattern. Default it so existing users see no behavior change from what the Explore page shows today.
• Profile read/write hooks — mirror the existing useProfileQuery read pattern and whatever mutation shape was established for updating active_group_id.
• Explore Set page's set-card header (or wherever it formats times) — read the persisted preference instead of a fixed/absent default.
• A settings route/page (existing or newly created per above) — hosts a toggle control bound to this preference.

Acceptance criteria:

• A persisted field for the 12/24-hour preference exists on the user's profile, following the active_group_id pattern.
• The Explore Set page reads this persisted preference instead of having no source for it.
• A toggle for this preference exists in a real settings surface — either a pre-existing one (if Active Group: app-wide group perspective/scope for votes #122 landed first) or a new minimal one created by this ticket — reachable from normal app navigation, not a dev-only/prototype route.
• Toggling the preference updates the Explore Set page's displayed time format without a reload.
• A logged-out/no-profile user sees a sensible fallback rather than a crash.

Out of scope:

• Building out the rest of Active Group: app-wide group perspective/scope for votes #122's settings view or epic (group switcher, Vote Perspective/Scope settings, etc.) — only a minimal home for this one toggle if nothing exists yet.
• Consolidating SetDetails/Vote tab's URL-param-based use24Hour or the Artists tab context's local default onto this persisted preference — those are separate, pre-existing inconsistencies not part of this ticket.
• Final visual design of the eventual full settings view — an interim minimal page is expected to be replaced or absorbed later.

Blocked by: nothing — proceed even if #122 hasn't landed, per the fallback behavior above. Check #122/PR #288's status first so a real settings surface isn't duplicated if it already exists.

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Generated by Claude Code