Offline mode

The cleaner app is a PWA with a service worker — it works when the device is offline.

What runs offline

• Reading the current task's checklist (cached when the app first loaded).
• Marking items done, skipped, with photos or notes.
• Reporting an issue (photos + voice + text — all queued locally).
• Bulk-mark (queues per-item completions).

What does NOT run offline

• Opening a different task (the dispatch link needs the server).
• Login (OTP needs the server).
• Sending the operator digest (queued; sent on reconnect with timestamp = original completion time).

Sync indicator

The header shows one of three states:

• Online — all writes go straight to the server.
• Offline · N changes queued — N writes waiting locally.
• Syncing… N left — reconnect in progress, draining the queue.

What the cleaner sees on reconnect

When the device comes back online, the queue drains in order. Each write keeps its original timestamp — the server records the action as having happened when the cleaner did it, not when sync ran.

If a write fails on the server (rare — e.g. the task was already closed by the operator), the cleaner sees a toast: 1 change couldn't sync — tap to see details. Tapping opens a per-change view with the reason; the cleaner can copy the photos out before the local queue clears.

What about the basement lift

Designed for exactly this case: signal drops in the basement, cleaner keeps marking items, reception comes back at the lobby. No data lost.

The queue is bounded — up to 200 actions or 50 MB of media. Above that, the oldest queued non-photo actions drop first (photos always preserved). In practice this only matters if the cleaner stayed offline for hours; a typical cleaning hits 20-30 actions.

Implements: gh#524 Slice 3 (offline queue + service worker).