Add system view fallback (#18536)

## Context
The goal is to add a "See records" button in all objects that would
redirect to that view (this will be done in a later PR). See screenshot
below.
<img width="665" height="312" alt="Screenshot 2026-03-10 at 15 54 36"
src="https://github.com/user-attachments/assets/6e23a75b-cff0-4d93-bce8-b5481b05c6f6"
/>

## Implementation
- If a view does not exist on an object, there is a **temporary**
fallback where the frontend creates the missing view as a custom view
when going over the object index page
- System objects are now surfaced but we don't want their records to be
editable, they will be readonly (mostly, all fields will be non-editable
except for their custom fields).
- We can't create a new record of a system object, some actions are also
hidden.
- The backend now rejects if you are trying to delete the last view of
an object

packages/twenty-front/src/modules/object-record/read-only/hooks/useIsRecordFieldReadOnly.ts

@@ -41,6 +41,7 @@ export const useIsRecordFieldReadOnly = ({
 
   return isRecordFieldReadOnly({
     isRecordReadOnly,
+    isSystemObject: objectMetadataItem.isSystem,
     objectPermissions,
     fieldMetadataItem,
   });

packages/twenty-front/src/modules/object-record/read-only/utils/__tests__/isRecordFieldReadOnly.test.ts

@@ -23,6 +23,7 @@ describe('isRecordFieldReadOnly', () => {
       fieldMetadataItem: {
         id: 'field-123',
         isUIReadOnly: false,
+        isCustom: false,
       },
     });
 
@@ -39,6 +40,7 @@ describe('isRecordFieldReadOnly', () => {
       fieldMetadataItem: {
         id: 'field-123',
         isUIReadOnly: false,
+        isCustom: false,
       },
     });
 
@@ -57,6 +59,7 @@ describe('isRecordFieldReadOnly', () => {
       fieldMetadataItem: {
         id: 'field-123',
         isUIReadOnly: false,
+        isCustom: false,
       },
     });
 
@@ -69,6 +72,7 @@ describe('isRecordFieldReadOnly', () => {
       fieldMetadataItem: {
         id: 'field-123',
         isUIReadOnly: true,
+        isCustom: false,
       },
     });
 
@@ -81,6 +85,48 @@ describe('isRecordFieldReadOnly', () => {
       fieldMetadataItem: {
         id: 'field-123',
         isUIReadOnly: false,
+        isCustom: false,
+      },
+    });
+
+    expect(result).toBe(false);
+  });
+
+  it('should return true when field is non-custom on a system object', () => {
+    const result = isRecordFieldReadOnly({
+      ...mockParams,
+      isSystemObject: true,
+      fieldMetadataItem: {
+        id: 'field-123',
+        isUIReadOnly: false,
+        isCustom: false,
+      },
+    });
+
+    expect(result).toBe(true);
+  });
+
+  it('should return false when field is custom on a system object', () => {
+    const result = isRecordFieldReadOnly({
+      ...mockParams,
+      isSystemObject: true,
+      fieldMetadataItem: {
+        id: 'field-123',
+        isUIReadOnly: false,
+        isCustom: true,
+      },
+    });
+
+    expect(result).toBe(false);
+  });
+
+  it('should return false when isSystemObject is not provided', () => {
+    const result = isRecordFieldReadOnly({
+      ...mockParams,
+      fieldMetadataItem: {
+        id: 'field-123',
+        isUIReadOnly: false,
+        isCustom: false,
       },
     });
 

packages/twenty-front/src/modules/object-record/read-only/utils/isRecordFieldReadOnly.ts

@@ -4,13 +4,18 @@ import { type ObjectPermission } from '~/generated-metadata/graphql';
 
 type IsRecordFieldReadOnlyParams = {
   isRecordReadOnly: boolean;
-  fieldMetadataItem: Pick<FieldMetadataItem, 'id' | 'isUIReadOnly'>;
+  isSystemObject?: boolean;
+  fieldMetadataItem: Pick<
+    FieldMetadataItem,
+    'id' | 'isUIReadOnly' | 'isCustom'
+  >;
   objectPermissions: ObjectPermission;
 };
 
 export const isRecordFieldReadOnly = ({
   objectPermissions,
   isRecordReadOnly,
+  isSystemObject,
   fieldMetadataItem,
 }: IsRecordFieldReadOnlyParams) => {
   const fieldReadOnlyByPermissions = isFieldMetadataReadOnlyByPermissions({
@@ -20,6 +25,7 @@ export const isRecordFieldReadOnly = ({
 
   return (
     isRecordReadOnly ||
+    (isSystemObject === true && fieldMetadataItem.isCustom !== true) ||
     fieldMetadataItem.isUIReadOnly ||
     fieldReadOnlyByPermissions
   );