Add email thread widget and message thread record page layout (#19351)

## Summary
- Move email thread display from side panel to a dedicated record page
with a new `EMAIL_THREAD` widget type
- Add message thread as a standard object with page layout, subject
field, and backfill command
- Add reply-to-email command menu item for message thread records
- Remove old side panel message thread components in favor of the new
widget-based approach

## Type fixes
- Add `EMAIL_THREAD` to `WidgetConfigurationType`, `WidgetType`, and all
configuration/validator maps
- Create `EmailThreadConfigurationDTO` and shared
`EmailThreadConfiguration` type
- Register EMAIL_THREAD in widget type validators, configuration
resolvers, and standard widget mappings

## Test plan
- [ ] Verify message thread record pages render with the email thread
widget
- [ ] Verify email thread preview navigates to the record page instead
of opening side panel
- [ ] Verify reply-to-email command appears for message thread records
- [ ] Verify typecheck passes for both twenty-front and twenty-server
- [ ] Run existing test suites to check for regressions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/twenty-server/src/engine/metadata-modules/page-layout-widget/constants/all-widget-configuration-type-validator-by-widget-configuration-type.constant.ts

@@ -1,4 +1,5 @@
 import { AggregateChartConfigurationDTO } from 'src/engine/metadata-modules/page-layout-widget/dtos/aggregate-chart-configuration.dto';
+import { EmailThreadConfigurationDTO } from 'src/engine/metadata-modules/page-layout-widget/dtos/email-thread-configuration.dto';
 import { BarChartConfigurationDTO } from 'src/engine/metadata-modules/page-layout-widget/dtos/bar-chart-configuration.dto';
 import { CalendarConfigurationDTO } from 'src/engine/metadata-modules/page-layout-widget/dtos/calendar-configuration.dto';
 import { EmailsConfigurationDTO } from 'src/engine/metadata-modules/page-layout-widget/dtos/emails-configuration.dto';
@@ -35,6 +36,7 @@ export const ALL_WIDGET_CONFIGURATION_TYPE_VALIDATOR_BY_WIDGET_CONFIGURATION_TYP
     CALENDAR: CalendarConfigurationDTO,
     FRONT_COMPONENT: FrontComponentConfigurationDTO,
     EMAILS: EmailsConfigurationDTO,
+    EMAIL_THREAD: EmailThreadConfigurationDTO,
     FIELD: FieldConfigurationDTO,
     FIELD_RICH_TEXT: FieldRichTextConfigurationDTO,
     FIELDS: FieldsConfigurationDTO,

packages/twenty-server/src/engine/metadata-modules/page-layout-widget/dtos/email-thread-configuration.dto.ts

@@ -0,0 +1,14 @@
+import { Field, ObjectType } from '@nestjs/graphql';
+
+import { IsIn, IsNotEmpty } from 'class-validator';
+import { type EmailThreadConfiguration } from 'twenty-shared/types';
+
+import { WidgetConfigurationType } from 'src/engine/metadata-modules/page-layout-widget/enums/widget-configuration-type.type';
+
+@ObjectType('EmailThreadConfiguration')
+export class EmailThreadConfigurationDTO implements EmailThreadConfiguration {
+  @Field(() => WidgetConfigurationType)
+  @IsIn([WidgetConfigurationType.EMAIL_THREAD])
+  @IsNotEmpty()
+  configurationType: WidgetConfigurationType.EMAIL_THREAD;
+}

packages/twenty-server/src/engine/metadata-modules/page-layout-widget/enums/widget-configuration-type.type.ts

@@ -27,6 +27,7 @@ export enum WidgetConfigurationType {
   WORKFLOW_RUN = 'WORKFLOW_RUN',
   FRONT_COMPONENT = 'FRONT_COMPONENT',
   RECORD_TABLE = 'RECORD_TABLE',
+  EMAIL_THREAD = 'EMAIL_THREAD',
 }
 export type AllGraphWidgetConfigurationType =
   | WidgetConfigurationType.AGGREGATE_CHART

packages/twenty-server/src/engine/metadata-modules/page-layout-widget/enums/widget-type.enum.ts

@@ -17,4 +17,5 @@ export enum WidgetType {
   WORKFLOW_RUN = 'WORKFLOW_RUN',
   FRONT_COMPONENT = 'FRONT_COMPONENT',
   RECORD_TABLE = 'RECORD_TABLE',
+  EMAIL_THREAD = 'EMAIL_THREAD',
 }