feat(competitions): calendar events, country selector, non-empty default

[AnayDhawan]

Blocked by #195 and #200.

Competition dates become calendar events, alongside the exam sessions and personal events already there.

Files

• src/app/calendar/CalendarView.tsx - extend, currently 478 lines
• src/lib/competition-events.ts - new, flattens competitions into calendar events

What exists today

CalendarView.tsx is a hand-rolled month grid with no date library, and that stays true. Plain Date, plain CSS Grid.

• :25-29 BOARD_COLORS for SAT, IB, IGCSE
• :31 PERSONAL_EVENT_COLOR
• :61-71 getEventsInMonth
• :91-104 getActiveDaysForEvent handles multi-day windows
• :201-205 builds the day cell array
• :380-464 the grid itself, colored dots per board

Two event sources today: the static EXAM_EVENTS array (src/lib/exam-dates.ts) and the user_events Supabase table. Competitions is the third. Add a COMPETITION_EVENT_COLOR next to the existing constants.

The density problem, which has to be designed for rather than discovered

50 competitions with roughly 4 dates each, plus 13 country tracks with roughly 3 stages each, is well over 2000 potential events. Dropping all of that onto a month grid makes it unusable, particularly on mobile.

Three controls, in this order of importance:

1. Signed-in users with at least one save default to saved competitions only, with a toggle to show all.
2. Everyone else defaults to all competitions filtered to their country, never to an empty grid. This matters: a saved-only default would give every new and signed-out visitor a blank calendar, and an empty first screen is a bad first screen.
3. Country tracks render one country at a time. Default to the country on the user's profile (feat(onboarding): user_profiles table with RLS and CHECK constraints (SQL inline) #203) when present, otherwise a picker defaulting to a sensible guess. Never render all 13 at once.

Estimated dates

The estimated flag exists on every date and stage in the dataset. Render those visibly differently from confirmed ones: an outline dot rather than a filled one, and say so in the legend. ExamEvent already carries the same idea via resultsEstimated (src/lib/exam-dates.ts:13-29), so follow whatever that does.

Acceptance criteria

• Competition dates appear on the correct days in the correct month
• Signed out: the calendar is not empty, and shows country-scoped competitions
• Signed in with saves: defaults to saved only, toggle reveals all
• Signed in with no saves: does not show an empty grid
• Only one country's stages render at a time
• Estimated dates are visually distinct and explained in the legend
• A day with many events stays legible at 360px wide
• Month navigation stays smooth with all competitions shown
• Supabase unconfigured: exam events and competitions still render, personal events and the saved filter are absent

[yakew7]

Implemented in a709121.

• src/lib/competition-events.ts: competitionEvents flattens a competition's own dates[] plus (only when a country is given) that country's country_tracks stages; competitionEventsInMonth filters to a calendar month; competitionsForCountry scopes the dataset to what's relevant for one country (international, region match, or a real qualifier track), which is what keeps the signed-out/no-saves default non-empty without dumping everything on the grid.
• CalendarView.tsx: competitions are a third event source alongside EXAM_EVENTS and user_events, with a new COMPETITION_EVENT_COLOR next to the existing board/personal-event colors. Signed-in users with at least one save default to saved-only with a toggle to the same country-scoped "all" view everyone else gets; that toggle only appears once there's at least one save. Country tracks render one country at a time via a picker in the controls row.
• Density: a day's competition dot is capped to "confirmed present" / "estimated present" regardless of how many of the ~2000 possible events land on it that day, so a busy month stays legible at 360px. Estimated dates get an outline dot instead of filled, both on the grid and in the new "Competitions this month" list, and the legend explains it.
• No date library added, per the issue - plain Date and the file's existing month-grid math throughout.

Process note, matching #196/#197: this issue references #203's signed-in profile country as the eventual default for the country picker, but #203 hasn't landed yet in the chain (it's next), so the picker currently starts on a fixed sensible guess ("IN", given StudyMap's own userbase) with a working picker to change it - not a hard blocker per the issue's own "Blocked by" field, which only lists #195 and #200.

13 new tests (competition-events.ts's pure functions, plus CalendarView behavior with Supabase/competition-saves mocked - the non-empty signed-out state, the toggle's visibility gated on having saves, the country picker's default). Full suite (258 tests), typecheck, lint and build all pass; a running dev server confirms the new section, picker, and legend entries render correctly.