[codex] Add WCIF v2 round support

[coder13]

Summary

• switch WCIF fetch and patch calls to /api/v0/competitions/{id}/wcif/version/2
• add a local WCIF v2 compatibility layer for participationRuleset and linkedRounds until @wca/helpers is updated
• derive legacy round participation and advancement semantics so dual-round setups such as Clock continue to work in the existing UI and validation flows

Why

The app was still typed and wired for the older WCIF shape. WCIF v2 moves round progression and participation details into new fields, which broke assumptions around registration-based second rounds and linked-round advancement.

Impact

This lets the dashboard consume WCIF v2 data now, including dual-round Clock configurations like MNHeartlandWarmUpII2026, without waiting for the helper package release.

Validation

• yarn test src/lib/api/wcaAPI.test.ts src/lib/wcif/rounds.test.ts src/lib/domain/persons.test.ts src/lib/wcif/validation/eventRoundValidation.test.ts
• yarn check:type
• repo commit hook: vitest run
• repo pre-push checks: tsc --noEmit, eslint ./