fix: keep group ratio input as string draft to allow decimal typing (#5995)

The ratio column normalized input to number on every keystroke, so
typing 0.05 got stuck at 0.0 which Number() collapses to 0. Keep the
value as a string draft like the top-up ratio column and only convert
to number when serializing.

Fixes #5986

web/default/src/features/system-settings/models/group-ratio-visual-editor.tsx

@@ -83,7 +83,7 @@ type GroupRatioVisualEditorProps = {
 type GroupPricingRow = {
   _id: string
   name: string
-  ratio: number
+  ratio: string
   topupRatio: string
   selectable: boolean
   description: string
@@ -149,7 +149,7 @@ function buildGroupPricingRows(
   return [...names].map((name) => ({
     _id: createGroupPricingId(),
     name,
-    ratio: normalizeRatio(ratioMap[name]),
+    ratio: String(normalizeRatio(ratioMap[name])),
     topupRatio: Object.hasOwn(topupMap, name) ? String(topupMap[name]) : '',
     selectable: Object.hasOwn(usableMap, name),
     description: String(usableMap[name] ?? ''),
@@ -491,7 +491,7 @@ function GroupPricingTable({
       {
         _id: createGroupPricingId(),
         name,
-        ratio: 1,
+        ratio: '1',
         topupRatio: '',
         selectable: true,
         description: '',
@@ -567,13 +567,9 @@ function GroupPricingTable({
                     type='number'
                     min={0}
                     step={0.1}
-                    value={String(row.ratio)}
+                    value={row.ratio}
                     onChange={(event) =>
-                      updateRow(
-                        row._id,
-                        'ratio',
-                        normalizeRatio(event.target.value)
-                      )
+                      updateRow(row._id, 'ratio', event.target.value)
                     }
                   />
                 ),