fix: route polyline visibility + login URL

B1: Add ResizeObserver to MapView.jsx to handle layout settling.
The map canvas had 0 height at init because layout hadnt settled
when the useEffect fired. ResizeObserver calls map.resize() on
any container size change.

B11: Use native outpost start URL for login initiation:
/outpost.goauthentik.io/start?rd=%2F
This properly triggers auth flow and redirects to / after login.
Removed the Caddy /login handler that wasnt redirecting correctly.

src/components/MapView.jsx

@@ -1046,7 +1046,14 @@ const MapView = forwardRef(function MapView(_, ref) {
 
     mapInstance.current = map
 
+    // ResizeObserver to handle layout settling, panel changes, window resize
+    const ro = new ResizeObserver(() => {
+      map.resize()
+    })
+    ro.observe(mapRef.current)
+
     return () => {
+      ro.disconnect()
       if (watchIdRef.current != null) navigator.geolocation.clearWatch(watchIdRef.current)
       if (gpsMarkerRef.current) gpsMarkerRef.current.remove()
       maplibregl.removeProtocol('pmtiles')