[stevenphanny]

What changed

This PR strengthens MAC Study’s database, data-access and testing foundations while preserving existing application behaviour.

• Added CI checks for linting, typechecking, unit tests, production builds and dependency vulnerabilities.
• Added repeatable local Supabase resets to verify every migration from an empty database.
• Generated database types and applied them to all Supabase clients.
• Split the large app-data.ts module into timer, units, groups, friends, chat and notifications modules.
• Replaced broad social snapshot queries with focused RPCs, pagination and aggregate queries.
• Scoped client caches per user and added freshness, request deduplication and mutation/realtime invalidation.
• Consolidated dashboard realtime subscriptions and paused loading for hidden dashboards.
• Added Playwright coverage for authentication, starting a timer, creating a group and RLS-protected access.

Validation

• ESLint
• TypeScript typecheck
• Vitest unit tests
• Next.js production build
• Fresh Supabase migration reset
• Generated database types check
• Playwright critical browser flows
• All three GitHub Actions jobs passing