Add applicationId to syncableEntity and fix syncApp deletion (#15170)

## Context
- All flatEntity should extend SyncableEntity
- SyncableEntity should now have applicationId and application relation
- Fix syncApp deletion, should now properly use migration v2 to delete
syncable entities

packages/twenty-server/src/engine/metadata-modules/flat-index-metadata/__mocks__/get-flat-index-metadata.mock.ts

@@ -23,6 +23,7 @@ export const getFlatIndexMetadataMock = (
     name: 'defaultFlatIndexMetadataName',
     updatedAt: createdAt,
     workspaceId: faker.string.uuid(),
+    applicationId: faker.string.uuid(),
     ...overrides,
   };
 };

packages/twenty-server/src/engine/metadata-modules/flat-index-metadata/types/flat-index-metadata.type.ts

@@ -1,3 +1,4 @@
+import { type FlatEntityFrom } from 'src/engine/metadata-modules/flat-entity/types/flat-entity.type';
 import { type IndexFieldMetadataEntity } from 'src/engine/metadata-modules/index-metadata/index-field-metadata.entity';
 import { type IndexMetadataEntity } from 'src/engine/metadata-modules/index-metadata/index-metadata.entity';
 import { type ExtractRecordTypeOrmRelationProperties } from 'src/engine/workspace-manager/workspace-migration-v2/types/extract-record-typeorm-relation-properties.type';
@@ -9,6 +10,7 @@ export type IndexMetadataRelationProperties =
     MetadataEntitiesRelationTarget
   >;
 
+// Can't use FlatEntityFrom here because IndexFieldMetadataEntity is not a SyncableEntity
 export type FlatIndexFieldMetadata = Omit<
   IndexFieldMetadataEntity,
   ExtractRecordTypeOrmRelationProperties<
@@ -17,7 +19,7 @@ export type FlatIndexFieldMetadata = Omit<
   >
 >;
 
-export type FlatIndexMetadata = Omit<
+export type FlatIndexMetadata = FlatEntityFrom<
   IndexMetadataEntity,
   IndexMetadataRelationProperties
 > & {