P3: routes (selected, fallback, queried)

Backend
- api/routes.rs models the Babel-style route shape; metric uses an
  untagged enum to round-trip both numeric hop counts and the
  literal "infinite" string the daemon emits for poisoned routes
- routes_snapshot() runs the three GETs concurrently with try_join
  so the snapshot is internally consistent
- poller spawns a second 5s loop emitting routes://updated; both
  loops are owned by the Poller and aborted together on stop_daemon

Frontend
- routes store mirrors the snapshot shape; tabbed view (radix-vue)
  with selected, fallback and queried lists
- RouteTable component shared by selected/fallback; metric column
  is colour-coded (0 green, low neutral, high yellow, infinite red)
- Queried subnets show a live `expires in 12s` countdown driven by
  a 1Hz tick ref instead of mutating the store

src-tauri/src/lib.rs

@@ -39,6 +39,7 @@ pub fn run() {
             commands::peer_add,
             commands::peer_remove,
             commands::peers_stats,
+            commands::routes_snapshot,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");