fix: enable save button when changing currency default value (#16864)

Closes #16792

## Problem

When editing a currency field’s default value (for example, changing
from **USD** to **UYU**), the **Save** button remained disabled.
However, if the format setting was changed first (**short → full →
short**), the Save button would then work correctly for currency
changes.

## Root Cause

The form was using **React Hook Form’s `values` mode**, which did not
properly track dirty state for the `defaultValue` and `settings` fields.

## Solution

Switched to the **`defaultValues` + `reset()`** pattern:

- Initialize the form with `defaultValues` (using placeholder values)
- Call `reset()` when `fieldMetadataItem` loads

This correctly tracks dirty state by comparing against the most recent
`reset` values.

## Note

A similar pattern is used in:
- `useWebhookForm`
- `useImapSmtpCaldavConnectionForm`

Those hooks call `reset()` via query callbacks. In this case, `reset()`
is called inside a `useEffect` because the data comes from synchronous
Recoil state rather than an async query.

Found two solutions to the problem, created commits for both. I feel the
useEffect pattern makes more sense here since it's cleaner in terms of
code.

---------

Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/twenty-front/src/pages/settings/data-model/SettingsObjectFieldEdit.tsx

@@ -43,6 +43,7 @@ import { Section } from 'twenty-ui/layout';
 import { FieldMetadataType } from '~/generated-metadata/graphql';
 import { useNavigateApp } from '~/hooks/useNavigateApp';
 import { useNavigateSettings } from '~/hooks/useNavigateSettings';
+import { getFieldMetadataItemInitialValues } from '~/pages/settings/data-model/utils/getFieldMetadataItemInitialValues';
 
 //TODO: fix this type
 export type SettingsDataModelFieldEditFormValues = z.infer<
@@ -107,6 +108,9 @@ export const SettingsObjectFieldEdit = () => {
   const getRelationMetadata = useGetRelationMetadata();
   const { updateOneFieldMetadataItem } = useUpdateOneFieldMetadataItem();
 
+  const { settings, defaultValue } =
+    getFieldMetadataItemInitialValues(fieldMetadataItem);
+
   const formConfig = useForm<SettingsDataModelFieldEditFormValues>({
     mode: 'onTouched',
     resolver: zodResolver(settingsFieldFormSchema()),
@@ -116,7 +120,8 @@ export const SettingsObjectFieldEdit = () => {
       label: fieldMetadataItem?.label ?? '',
       description: fieldMetadataItem?.description,
       isLabelSyncedWithName: fieldMetadataItem?.isLabelSyncedWithName ?? true,
-      settings: fieldMetadataItem?.settings,
+      settings,
+      defaultValue,
     },
   });
 

packages/twenty-front/src/pages/settings/data-model/utils/getFieldMetadataItemInitialValues.ts

@@ -0,0 +1,35 @@
+import { type FieldMetadataItem } from '@/object-metadata/types/FieldMetadataItem';
+import { isNonEmptyString } from '@sniptt/guards';
+import { CurrencyCode } from 'twenty-shared/constants';
+import { FieldMetadataType } from '~/generated-metadata/graphql';
+import { DEFAULT_DECIMAL_VALUE } from '~/utils/format/formatNumber';
+import { applySimpleQuotesToString } from '~/utils/string/applySimpleQuotesToString';
+
+export const getFieldMetadataItemInitialValues = (
+  fieldMetadataItem: FieldMetadataItem | undefined,
+) => {
+  if (fieldMetadataItem?.type !== FieldMetadataType.CURRENCY) {
+    return {
+      settings: fieldMetadataItem?.settings ?? undefined,
+      defaultValue: fieldMetadataItem?.defaultValue ?? undefined,
+    };
+  }
+
+  const settings = fieldMetadataItem.settings ?? {
+    format: 'short',
+    decimals: DEFAULT_DECIMAL_VALUE,
+  };
+
+  const currencyCode = isNonEmptyString(
+    fieldMetadataItem.defaultValue?.currencyCode,
+  )
+    ? fieldMetadataItem.defaultValue?.currencyCode
+    : applySimpleQuotesToString(CurrencyCode.USD);
+
+  const defaultValue = {
+    amountMicros: fieldMetadataItem.defaultValue?.amountMicros ?? null,
+    currencyCode,
+  };
+
+  return { settings, defaultValue };
+};