Add companion auto-refresh settings

[shiny-code-bot]

Summary

• add a shared companion auto-update setting with 5/10/15/30/60 minute choices, defaulting to 5 minutes for the foreground companion app
• make the iOS/iPadOS/visionOS companion app reload on launch, foreground activation, manual refresh, and the configured foreground cadence
• make the companion widget read the same setting while enforcing a 15-minute WidgetKit floor, and reload widget timelines when the setting changes
• surface shared-storage/save failures in the companion settings UI and avoid split app/widget settings state when the app group is unavailable

Validation

• swift test --filter 'ContextPanelCoreTests.companionRefreshSettings'
• scripts/validate-companion-builds.sh ios
• scripts/validate-companion-builds.sh visionos
• scripts/commit-gate.sh

Review notes

• Shape review and final review agents checked the app-group storage path, save failure handling, WidgetKit cadence floor, redundant timeline reloads, privacy/storage, target wiring, and release risk.
• The companion app can prefer 5-minute foreground refreshes; the widget timeline policy intentionally uses at least 15 minutes because WidgetKit treats refresh dates as budgeted hints.