docs: complete v1.2 research (stack, features, architecture, pitfalls)
- STACK.md: google-auth-library@10.7.0 + @googleapis/calendar@15.0.0 scoped packages (vs monolithic googleapis), OAuth2 flow, token storage, Google Calendar API event/reminder model
- FEATURES.md: 6 feature categories (multi-provider, self-service onboarding, multiple reminders, dark mode, zero-setup DB, dev/CI stub), dependency graph, feature prioritization
- ARCHITECTURE.md: CalendarProvider interface, provider factory, CalDavProvider wrapper, GoogleCalendarProvider, MockProvider, provider_tokens table schema, multi-reminder JSON column, OAuth callback routing, 7-component data flows
- PITFALLS.md: 11 critical/medium pitfalls (refresh token 7-day expiry in testing status, Google recurrence mismatch, syncToken 410, timezone handling, provider abstraction regression, VALARM dedup key, auto-migrate failures, dark mode FOWT, OAuth callback through tunnel, token encryption, ESLint 10 breaking changes)
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
