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-field-metadata/__mocks__/get-flat-field-metadata.mock.ts

@@ -43,7 +43,7 @@ export const getFlatFieldMetadataMock = <T extends FieldMetadataType>(
     standardId: null,
     standardOverrides: null,
     workspaceId: faker.string.uuid(),
-
+    applicationId: faker.string.uuid(),
     relationTargetFieldMetadataId: null,
     relationTargetObjectMetadataId: null,
     ...overrides,

packages/twenty-server/src/engine/metadata-modules/flat-field-metadata/__mocks__/get-morph-or-relation-target-flat-field-metadata-mock.ts

@@ -62,5 +62,6 @@ export const getRelationTargetFlatFieldMetadataMock = ({
     ...overrides,
     defaultValue: null,
     options: null,
+    applicationId: faker.string.uuid(),
   };
 };