web: put the white and black points on the LIGHT tab

WHITE (whites) and BLACK (blacks) get the same slider rows as HIGHLIGHT
and SHADOW, so the tone curve's two ends are editable on the stage, not
only typed into the CREATE form.

docker/frontend/shared/utils/paramDefs.ts

@@ -105,6 +105,30 @@ export const PARAM_DEFS: {
       get: (a) => a.shadow ?? 0,
       set: (v) => ({ shadow: v }),
     },
+    {
+      // The end points of the tone curve: WHITE lifts/crushes the top, BLACK the
+      // toe. Same range as the CREATE form's rows, so a look round-trips.
+      key: 'whites',
+      label: 'WHITE',
+      min: -10,
+      max: 10,
+      step: 1,
+      defaultValue: 0,
+      display: sign,
+      get: (a) => a.whites ?? 0,
+      set: (v) => ({ whites: v }),
+    },
+    {
+      key: 'blacks',
+      label: 'BLACK',
+      min: -10,
+      max: 10,
+      step: 1,
+      defaultValue: 0,
+      display: sign,
+      get: (a) => a.blacks ?? 0,
+      set: (v) => ({ blacks: v }),
+    },
   ],
   wb: [
     {