fix(sync): show device-approval prompt after reconnect (replay pending transfers)

[khokonm]

Problem

When a new device joins a sync chain, it asks an existing device to send it the notes (peer transfer with approval). The other devices were never showing the approval prompt — not while they were active, and not when they reopened the app later.

Root cause

The approval request was delivered fire-and-forget:

1. New device → request-transfer-from → the server creates a pending transfer row and calls sendToDevice(target, { type: 'transfer-requested' }).
2. sendToDevice only delivers if the target has a live WebSocket at that exact moment; its boolean return is ignored and a missed message is lost.
3. The join/welcome handler never replays pending transfer requests when a device (re)connects.

On mobile PWAs the WebSocket drops whenever the app is backgrounded or the screen locks, so an "active" phone usually isn't holding a live socket — the request is dropped, and because nothing re-delivers it, reopening the app ("returning") shows nothing either. db.ts already had getPendingTransfers() written for this case, but it was dead code — never imported or called.

Fix

Wire getPendingTransfers() into the join handler. When an established device (re)connects, the server replays any still-pending transfer requests in its room, so the approval prompt appears as soon as the device has a live connection.

Guards:

• Only status === 'pending' transfers (already-approved/in-flight ones are skipped).
• The requester is skipped (a device is never asked to approve its own request).
• Only replayed when the requester is currently online, so we don't prompt for a transfer whose new device has gone away.
• Brand-new (needsTransfer) devices are not asked to approve — they have no notes to send.

The existing immediate sendToDevice path is unchanged; this purely adds durable re-delivery on connect. Replaying a request the approver already saw is harmless (same transferId; the server still validates status === 'pending' on approve).

Files changed

• server/src/index.ts — import getPendingTransfers; replay pending transfer requests in the join handler.

Verification

• Reviewed against db.ts (getPendingTransfers returns rows with status IN ('pending','approved','in_progress'); TransferRecord.status includes 'pending') and the client handler (case 'transfer-requested' sets pendingTransfer, rendered by the global modal in App.tsx and the panel card in SettingsPanel.tsx).
• Not run locally: tsc/build/lint — the server's dependencies aren't installed in the sandbox and package installs are blocked (registry 403). The change is additive and uses only already-imported/in-scope symbols (getDevice, room, WebSocket).

Manual test plan

1. Device A (with notes) signed into a sync chain; Device B is new.
2. On B, enter the sync code and pick A as the source.
3. Active: with A's app open, confirm the approval prompt appears on A; approve → B receives notes.
4. Backgrounded/returns: trigger the request from B while A's app is closed/backgrounded, then open A → confirm the approval prompt now appears on A (previously it never did) → approve → B receives notes.
5. Deny path still works; approving/denying twice is a no-op (transfer no longer pending).