[LHagfoss]

What

Two fixes in Settings › Machines.

• A connected machine's route hint (for example "Not reachable over the VPN …") was drawn twice: machineLine appended it to the route line and the row drew it again on its own line. machineLine now returns the route only; the row's own hint line is the one place it shows.
• Machines found listed this computer. Bonjour hears the gateway this computer runs too. machines_discover now leaves out a record whose gateway id is this computer's, or one of whose addresses is bound on this computer's interfaces on its gateway port (read from remote/registration.json, else 17879).

Changelog

Settings › Machines says a machine's route problem once and no longer lists this computer under Machines found.

Testing

• bun run check in apps/desktop; new render test src/ui/MachinesPage.test.tsx asserts the hint appears once.
• cargo fmt --check, cargo clippy --all-targets -- -D warnings, cargo test machines::tests::this_computer in apps/desktop/src-tauri (covers the gateway-id and own-address matches).

Closes #3433
Closes #3432