20215 convert application variable to a syncable entity (#20269)

##  Summary

- Converts applicationVariable from a bespoke sync path to a proper
SyncableEntity,
unifying it with the workspace migration pipeline used by all other
manifest-managed
  entities (agent, skill, frontComponent, webhook, etc.)
- Removes the upsertManyApplicationVariableEntities method and its
direct-DB-mutation
approach in favor of the standard validate → build → run action handler
pipeline
- Adds universalIdentifier, deletedAt columns and makes applicationId
NOT NULL via an
  instance command migration

##  Motivation

Before this change, applicationVariable was the only manifest-managed
entity that bypassed
ApplicationManifestMigrationService.syncMetadataFromManifest(). It used
a bespoke service
method called directly from syncApplication(), creating two mental
models, two validation
styles, and two cache invalidation patterns. Now there's one unified
pipeline for all
  manifest entities.

##  What changed

###  Entity refactor:
- ApplicationVariableEntity now extends SyncableEntity (gains
universalIdentifier,
  non-nullable applicationId with CASCADE, soft-delete via deletedAt)

###  New flat entity layer (flat-application-variable/):
- Type, maps type, editable properties constant, entity-to-flat
converter, cache service,
  module

###  New migration pipeline wiring:
- Manifest converter
(fromApplicationVariableManifestToUniversalFlatApplicationVariable)
  - Validator service (FlatApplicationVariableValidatorService)
- Builder service
(WorkspaceMigrationApplicationVariableActionsBuilderService)
  - Create/Update/Delete action handlers with secret encryption hooks
- Registered in orchestrator, builder module, runner module, and all
type registries

###  Removed bespoke path:
- Deleted upsertManyApplicationVariableEntities from
ApplicationVariableEntityService
  - Removed its call from ApplicationSyncService.syncApplication()
- Kept update() (operator-set value at runtime) and getDisplayValue()
(runtime display)

###  Database migration:
- Instance command to add columns, backfill universalIdentifier, enforce
NOT NULL
  constraints, and update indexes

##  Test plan

  - npx nx typecheck twenty-server passes (0 errors)
- Unit tests pass (application-variable.service.spec.ts,
build-env-var.spec.ts)
- Install an app with applicationVariables in its manifest → variables
appear with correct
  universalIdentifier
- Update app manifest (add/remove/modify a variable) → migration
pipeline handles diff
  correctly
- Operator-set value via update endpoint persists correctly with
encryption
  - Uninstall app → variables cascade-deleted
  - app dev --once on example app syncs without errors

packages/twenty-server/src/engine/workspace-manager/workspace-migration/universal-flat-entity/constants/__tests__/__snapshots__/all-universal-flat-entity-foreign-key-aggregator-properties.constant.spec.ts.snap

@@ -3,6 +3,7 @@
 exports[`ALL_UNIVERSAL_FLAT_ENTITY_FOREIGN_KEY_AGGREGATOR_PROPERTIES should match snapshot 1`] = `
 {
   "agent": [],
+  "applicationVariable": [],
   "commandMenuItem": [],
   "connectionProvider": [],
   "fieldMetadata": [

packages/twenty-server/src/engine/workspace-manager/workspace-migration/universal-flat-entity/constants/all-jsonb-properties-with-serialized-relation-by-metadata-name.constant.ts

@@ -42,6 +42,7 @@ export const ALL_JSONB_PROPERTIES_WITH_SERIALIZED_RELATION_BY_METADATA_NAME = {
   objectPermission: {},
   fieldPermission: {},
   frontComponent: {},
+  applicationVariable: {},
   connectionProvider: {},
 } as const satisfies {
   [P in AllMetadataName]: Partial<{

packages/twenty-server/src/engine/workspace-manager/workspace-migration/universal-flat-entity/types/universal-flat-application-variable.type.ts

@@ -0,0 +1,7 @@
+import { type ApplicationVariableEntity } from 'src/engine/core-modules/application/application-variable/application-variable.entity';
+import { type UniversalFlatEntityFrom } from 'src/engine/workspace-manager/workspace-migration/universal-flat-entity/types/universal-flat-entity-from.type';
+
+export type UniversalFlatApplicationVariable = UniversalFlatEntityFrom<
+  ApplicationVariableEntity,
+  'applicationVariable'
+>;