feat(notifications): revenue recognition export, tz-aware quiet hours, digest batching, preferences entry point

[Dev-sandy1]

Summary

• Add revenue recognition export #1743 — Revenue recognition export: \exportRecognitionEntries\ flattens revenue schedules into per-period rows with accrual (ASC 606 pro-rating) or cash basis, filtered to any window, emitted as CSV or JSON; wired to export buttons on the Revenue Report screen and an \exportRecognitionEntries\ action in the accounting store.
• Add push notification scheduling #1744 — Timezone-aware quiet hours: push scheduling and delivery deferral now evaluate the quiet window in the subscriber's configured IANA timezone (DST-safe, Intl-based), instead of hard-coded UTC/device-local hours. Critical notifications still bypass quiet hours; UTC scheduling is preserved.
• Add email digest option #1746 — Email digest: when a subscriber chooses a daily/weekly digest, non-critical notifications are buffered and flushed as one grouped digest notification once its UTC window (09:00 UTC next day / next Monday) passes; \lushDigestNow/\maybeFlushDueDigest\ are exported for the host app to call on resume/foreground.
• Add a notification preferences center #1745 — Preferences center reachability: registered the \NotificationPreferences\ route in the root stack types and added a Settings row that opens the existing notification preferences screen (categories, channels, digest schedule, quiet hours).

Tests

• \src/services/tests/revenueRecognitionExport.test.ts\ (accrual pro-rating, cash basis, window filter, sorting, CSV/JSON, escaping)
• \src/services/tests/pushScheduleEngine.test.ts\ (UTC + Europe/Berlin quiet hours, DST boundaries, critical bypass, opt-in filter, digest windows, DigestBuilder grouping)
• \src/services/tests/notificationDigest.test.ts\ (buffering, grouped flush, critical bypass, auto-flush on window, immediate mode, digest-not-re-buffered)
• Existing
  otificationPreferencesStore\ suite (31 tests) still green.

Closes #1743
Closes #1744
Closes #1745
Closes #1746

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