testing: unit tests for user-places, user-events, utils.isMissingTableError, map.directionsUrl, exam-dates

[shauryagangrade]

Context

npm run test:unit covers geo/share/places/places-api/city-pages/jsonld/og/changelog/awesome-list, but several lib modules have zero coverage:

Module	What to test
src/lib/user-places.ts	mapping (userPlaceToPlace), error classification
src/lib/user-events.ts	CRUD payload shapes, date handling
src/lib/utils.ts	isMissingTableError() against real Postgres error shapes (code 42P01 etc.)
src/lib/map.ts	directionsUrl() output format
src/lib/exam-dates.ts	structural invariants: sorted dates, required fields, no past-dated events still marked upcoming

Supabase-dependent modules need the client mocked (vitest module mocking); the pure ones are trivial wins.

Acceptance criteria

• Each listed module has meaningful tests passing via npm run test:unit