Add offline reading and resilient cached content to the Expo app

[ThatXliner]

Goal

Make the Expo app useful and understandable when the device is offline or the network is unreliable, without showing a generic unrecoverable error screen.

MVP scope

• Persist the last successfully loaded Browse results on-device.
• Make previously opened bills, orders, cases, and briefings readable offline, including their summaries and source metadata.
• Cache content images on disk when practical; missing images must not block the detail screen.
• Show a clear offline/stale-data indicator and the time of the last successful refresh.
• Let search operate over cached content, or clearly explain when a server-only result is unavailable.
• Disable network-only actions with a specific explanation, or queue them safely for retry.
• Refresh stale data after connectivity returns without discarding usable cached content.

Technical considerations

• Choose and document the persistence layer (for example, persisted query cache for lightweight state and SQLite for durable searchable content).
• Bound storage with a documented size limit plus TTL/LRU eviction.
• Version the local schema/cache so app upgrades can migrate or safely invalidate it.
• Keep credentials and privileged data out of the content cache.
• Treat Supabase Storage images as independently cacheable assets rather than a prerequisite for rendering text.

Acceptance criteria

• After one successful online session, a cold launch in airplane mode reaches Browse and displays cached results.
• A previously opened content detail screen remains readable in airplane mode.
• Offline, empty, stale, and retry states are visually distinct and accessible.
• Reconnecting and refreshing replaces stale content without a restart.
• Automated tests cover cache hydration/invalidation, and a physical-device smoke test covers cold launch offline, intermittent connectivity, and reconnect.

Out of scope

• Downloading the entire corpus for offline use.
• Offline submission of feedback unless a durable retry queue is explicitly included in the implementation.