## Summary
- add a macOS local-network purpose string
- explain that LAN access is for optional Share Compute and local relay
connections
- clarify that messaging through a remote relay does not need it
## Context
macOS currently falls back to its generic Local Network prompt because
Buzz's `Info.plist` has no `NSLocalNetworkUsageDescription`. The alert
says Buzz can find and collect data from devices without explaining
which Buzz features use that capability, which makes an optional feature
feel invasive.
Buzz can intentionally make local-network connections for Share Compute
peers and user-configured local relays. Ordinary messaging through a
remote relay does not require that access.
Apple recommends that any app using the local network directly or
indirectly include `NSLocalNetworkUsageDescription`:
https://developer.apple.com/documentation/bundleresources/information-property-list/nslocalnetworkusagedescription
This PR improves the disclosure only. It does not change when macOS
asks. The exact unexpected trigger should be handled separately once it
can be reproduced and attributed.
## Verification
- `plutil -lint desktop/src-tauri/Info.plist`
- built a debug macOS `.app` bundle and confirmed its final `Info.plist`
contains the exact purpose string
- `just ci`
Signed-off-by: joelbrilliant <joelbrilliant1@gmail.com>
