fix(CSV export): update the csv export format for multi-select and arrray fields to match the import template format (#16450)

Closes #16432

Multi-Select and Array fields were exported in an incompatible format:
**Before**: {"0":"VALUE1","1":"VALUE2"} (object with numeric keys)
**After**: ["VALUE1","VALUE2"] (JSON array)

This prevented exported CSV files from being re-imported successfully.

### Changes
Modified useExportProcessRecordsForCSV hook to stringify Multi-Select
and Array fields as JSON arrays before CSV generation

---------

Co-authored-by: Etienne <45695613+etiennejouan@users.noreply.github.com>

packages/twenty-front/src/modules/object-record/object-options-dropdown/hooks/__tests__/useExportProcessRecordsForCSV.test.ts

@@ -9,6 +9,8 @@ jest.mock('@/object-metadata/hooks/useObjectMetadataItem', () => ({
       fields: [
         { type: FieldMetadataType.CURRENCY, name: 'price' },
         { type: FieldMetadataType.TEXT, name: 'name' },
+        { type: FieldMetadataType.MULTI_SELECT, name: 'tags' },
+        { type: FieldMetadataType.ARRAY, name: 'skills' },
       ],
     },
   })),
@@ -56,4 +58,82 @@ describe('useExportProcessRecordsForCSV', () => {
       },
     ]);
   });
+
+  it('processes records with multi-select and array fields correctly', () => {
+    const { result } = renderHook(() =>
+      useExportProcessRecordsForCSV('someObject'),
+    );
+
+    const records = [
+      {
+        __typename: 'ObjectRecord',
+        id: '1',
+        tags: ['TAG1', 'TAG2'],
+        skills: ['skill1', 'skill2', 'skill3'],
+        name: 'Item 1',
+      },
+      {
+        __typename: 'ObjectRecord',
+        id: '2',
+        tags: ['TAG3'],
+        skills: ['skill4'],
+        name: 'Item 2',
+      },
+    ];
+
+    let processedRecords;
+
+    act(() => {
+      processedRecords = result.current.processRecordsForCSVExport(records);
+    });
+
+    expect(processedRecords).toEqual([
+      {
+        __typename: 'ObjectRecord',
+        id: '1',
+        tags: '["TAG1","TAG2"]',
+        skills: '["skill1","skill2","skill3"]',
+        name: 'Item 1',
+      },
+      {
+        __typename: 'ObjectRecord',
+        id: '2',
+        tags: '["TAG3"]',
+        skills: '["skill4"]',
+        name: 'Item 2',
+      },
+    ]);
+  });
+
+  it('processes records with empty multi-select and array fields correctly', () => {
+    const { result } = renderHook(() =>
+      useExportProcessRecordsForCSV('someObject'),
+    );
+
+    const records = [
+      {
+        __typename: 'ObjectRecord',
+        id: '1',
+        tags: [],
+        skills: [],
+        name: 'Item 1',
+      },
+    ];
+
+    let processedRecords;
+
+    act(() => {
+      processedRecords = result.current.processRecordsForCSVExport(records);
+    });
+
+    expect(processedRecords).toEqual([
+      {
+        __typename: 'ObjectRecord',
+        id: '1',
+        tags: '[]',
+        skills: '[]',
+        name: 'Item 1',
+      },
+    ]);
+  });
 });

packages/twenty-front/src/modules/object-record/object-options-dropdown/hooks/useExportProcessRecordsForCSV.ts

@@ -29,6 +29,8 @@ export const useExportProcessRecordsForCSV = (objectNameSingular: string) => {
                   currencyCode: record[field.name].currencyCode,
                 } satisfies FieldCurrencyValue,
               };
+            case FieldMetadataType.MULTI_SELECT:
+            case FieldMetadataType.ARRAY:
             case FieldMetadataType.RAW_JSON:
               return {
                 ...processedRecord,