P1: profiles + decks migrations + RLS + deckRepository

[Doberjohn]

Cloud deck storage with owner-scoped RLS.

Scope

• Migration profiles (id → auth.users, handle unique-nullable, display_name, avatar_url), RLS public-read/owner-write + handle_new_user() signup trigger.
• Migration decks (id, owner_id, name, gameplan text?, inks text[] ≤2, cards jsonb = [{cardId,quantity,isCore}], is_public default false, slug unique) + updated_at trigger; RLS select using (is_public or auth.uid()=owner_id), insert/update/delete owner-only.
• deckRepository.ts CRUD (guarded by getSupabase()).
• Regenerate database.types.ts; run pnpm test:supabase + get_advisors.

Part of #451 · Deck Builder & Engine Score milestone.

[Doberjohn]

Delivered and merged into the deck-builder integration branch via #480 (not yet in production / master). Closing as complete; it rides to production when deck-builder later merges to master.