fix(dm): refresh mc.contacts from device on PATH_UPDATE event

The Contact Info dialog showed stale path data (e.g. "Flood" instead of
the discovered route) because auto_update_contacts is OFF and PATH_UPDATE
only sets _contacts_dirty=True without refreshing mc.contacts. The API
then served stale in-memory data even after cache invalidation.

Now ensure_contacts(follow=True) is called on PATH_UPDATE to read fresh
contact data from the device before invalidating cache and emitting the
socket event. PATH_UPDATE events are rare (only on path discovery), so
the serial I/O cost is acceptable unlike advertisements.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/device_manager.py

@@ -761,6 +761,14 @@ class DeviceManager:
             )
             logger.debug(f"Path update for {pubkey[:8]}...")
 
+            # Refresh mc.contacts from device so API returns fresh path data.
+            # PATH_UPDATE events are rare (only on path discovery), so the
+            # serial I/O cost is acceptable (unlike advertisements).
+            try:
+                await self.mc.ensure_contacts(follow=True)
+            except Exception as e:
+                logger.warning(f"Failed to refresh contacts after path update: {e}")
+
             # Invalidate contacts cache so UI gets fresh path data
             try:
                 from app.routes.api import invalidate_contacts_cache