feat(calendar): add private Google Calendar database view

[IsraelAraujo70]

What changed

• adds the calendar database contract and backward-compatible rich date values
• adds Google OAuth with PKCE, encrypted refresh tokens, per-user connections and source selection
• adds private event cache, incremental/full sync, webhook dedupe, recurring occurrence identity and an independent worker
• projects Google events, materialized meetings and manual date rows into one calendar endpoint
• materializes meeting notes through the existing operation engine with an idempotent event-to-row link
• adds month and week web views with timezone-aware event times, source settings, cancellation state and meeting popovers
• adds a native Expo/Android Agenda with month navigation, timezone-aware hours, all-day and cancelled states, event details, Meet links and linked-note navigation
• centralizes the calendar view patch and event projection contract in @reason/core so web and Android apply the same semantics
• adds a deterministic mobile Vitest gate and documents local, production and Android behavior

Why

Users can view the same selected Google calendars inside a database on web and Android without turning every event into a block. Private calendar data remains user-scoped, while explicit shared meeting notes remain normal database_row blocks.

Validation

• GitHub CI: Backend, Web, Core, mobile and desktop jobs passed
• make test: 162 Rust tests, 403 web tests, 5 mobile tests and 8 desktop tests passed
• shared core, mobile and desktop TypeScript builds passed
• clean mobile npm ci passed
• npx expo-doctor: 18/18 checks passed
• npx expo export --platform android: Android bundle completed with 1,278 modules
• git diff --check passed

Known dependency baseline

• npm audit --omit=dev reports 11 moderate and 19 high advisories in the existing Expo 54 / React Native toolchain. Available automated fixes require a major Expo 57 / React Native upgrade. This PR adds only Vitest as a development dependency and does not widen the Android runtime surface.

[chatgpt-codex-connector]

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