fix(server): preserve null values in record update util (#23639)

## Problem

Record updates through the MCP server silently drop `null` values.
Setting a field to `null` (to clear it) returns success but changes
nothing.

## Root cause

`removeUndefinedFromRecord` is called by `UpdateRecordService.execute`
before the DB write. It used `isDefined(value)` to decide what to strip,
but `isDefined` returns false for **both** `undefined` and `null`:

```ts
export const isDefined = (value) => !isUndefined(value) && !isNull(value);
```

So despite the name (and the comment stating the validation layer
expects "a value or null"), the util also discarded `null`. The MCP
`update_one` path deliberately keeps nulls (it filters only `!==
undefined`), but this util then removed them one layer down.

The workflow UPDATE_RECORD action was less affected because it passes an
explicit `fieldsToUpdate` list, but the value-level strip sits on both
paths.

## Fix

Strip only `undefined`; preserve `null` so a field can be explicitly
cleared. Added unit tests covering undefined stripping, null
preservation, and nested composite fields.

## Test

```
npx jest remove-undefined-from-record
# 5 passed
```

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packages/twenty-server/src/engine/core-modules/record-crud/utils/__tests__/remove-undefined-from-record.util.spec.ts

@@ -0,0 +1,40 @@
+import { removeUndefinedFromRecord } from 'src/engine/core-modules/record-crud/utils/remove-undefined-from-record.util';
+
+describe('removeUndefinedFromRecord', () => {
+  it('should strip undefined values', () => {
+    expect(removeUndefinedFromRecord({ name: 'John', age: undefined })).toEqual(
+      {
+        name: 'John',
+      },
+    );
+  });
+
+  it('should preserve null values so a field can be cleared', () => {
+    expect(
+      removeUndefinedFromRecord({ name: 'John', closeDate: null }),
+    ).toEqual({ name: 'John', closeDate: null });
+  });
+
+  it('should preserve null sub-properties in composite fields', () => {
+    expect(
+      removeUndefinedFromRecord({
+        emails: { primaryEmail: null, additionalEmails: undefined },
+      }),
+    ).toEqual({ emails: { primaryEmail: null } });
+  });
+
+  it('should drop nested objects that only contain undefined', () => {
+    expect(
+      removeUndefinedFromRecord({
+        emails: { primaryEmail: undefined },
+        name: 'John',
+      }),
+    ).toEqual({ name: 'John' });
+  });
+
+  it('should preserve arrays as-is', () => {
+    expect(
+      removeUndefinedFromRecord({ tags: ['a', 'b'], removed: undefined }),
+    ).toEqual({ tags: ['a', 'b'] });
+  });
+});

packages/twenty-server/src/engine/core-modules/record-crud/utils/remove-undefined-from-record.util.ts

@@ -1,5 +1,3 @@
-import { isDefined } from 'twenty-shared/utils';
-
 // Recursively removes undefined values from an object
 // This is needed because workflows/tools may pass partial composite fields
 // with undefined sub-properties, but the validation layer expects either
@@ -10,7 +8,7 @@ export const removeUndefinedFromRecord = <T extends Record<string, unknown>>(
   const result: Record<string, unknown> = {};
 
   for (const [key, value] of Object.entries(record)) {
-    if (!isDefined(value)) {
+    if (value === undefined) {
       continue;
     }