feat(frontend): add competition DTO store and browser

[aalonsolopez]

Problem or opportunity

The frontend needs stable types and selectors for multiple competitions instead of relying on LEC-specific shortcuts everywhere.

Proposed solution

Update src/store/types.ts, src/services/*, schedule pages, and tournament pages to consume competition DTOs and expose a selectable competition browser while preserving the LEC shortcut.

UX impact

Affected area: Frontend store/types/services and schedule/tournament views.

Acceptance criteria

• Frontend receives competition-aware DTOs.
• Users can select/browse supported competitions where relevant.
• Schedule and tournament views render the selected competition.
• Existing LEC shortcut/navigation remains functional.
• Props/selectors remain stable and testable.

Scope

UI / UX

Dependencies

Depends on competition runner and region selection.

Out of scope

International event automation and unrelated visual redesign.

Test notes

Add Vitest coverage for DTO mapping, selector behavior, competition selection, and LEC shortcut regression.

Approval pre-flight

• I searched existing issues and did not find a duplicate.
• I understand maintainers must add status:approved before implementation starts.
• I will branch from development using type/lowercase-slug if this is approved.
• I identified whether this changes docs, release behavior, licensing, or data provenance.

[NicoRuedaA]

WIP