Revert Leaflet’s maxBounds and its viscosity

They were commented out by error: when changing the SVG handling code,
had to “look for” a stray polygon that was outside the image’s bounded
area.

web/static/map.js

@@ -16,8 +16,8 @@
         maxZoom: 2,
         zoom: -1,
         scrollWheelZoom: false,
-        //maxBounds: latLngBounds,
-        //maxBoundsViscosity: 1.0,
+        maxBounds: latLngBounds,
+        maxBoundsViscosity: 1.0,
         zoomSnap: 0,
         crs: L.CRS.Simple,
     });