fix(core): Use consistent timezone-aware timestamps in postgres (#6948)

Fixes:
* ENG-51 / N8N-2490
* PAY-397
* #2178
* #2810
* #3855

Supersedes #2813

[DB
Tests](https://github.com/n8n-io/n8n/actions/runs/6000780146/job/16273596338)

packages/cli/src/databases/entities/AbstractEntity.ts

@@ -1,3 +1,4 @@
+import type { ColumnOptions } from 'typeorm';
 import {
 	BeforeInsert,
 	BeforeUpdate,
@@ -5,7 +6,6 @@ import {
 	PrimaryColumn,
 	UpdateDateColumn,
 } from 'typeorm';
-import { IsDate, IsOptional } from 'class-validator';
 import config from '@/config';
 import { generateNanoId } from '../utils/generators';
 
@@ -21,9 +21,10 @@ const timestampSyntax = {
 export const jsonColumnType = dbType === 'sqlite' ? 'simple-json' : 'json';
 export const datetimeColumnType = dbType === 'postgresdb' ? 'timestamptz' : 'datetime';
 
-const tsColumnOptions = {
+const tsColumnOptions: ColumnOptions = {
 	precision: 3,
 	default: () => timestampSyntax,
+	type: datetimeColumnType,
 };
 
 type Constructor<T> = new (...args: any[]) => T;
@@ -46,16 +47,9 @@ function mixinStringId<T extends Constructor<{}>>(base: T) {
 function mixinTimestamps<T extends Constructor<{}>>(base: T) {
 	class Derived extends base {
 		@CreateDateColumn(tsColumnOptions)
-		@IsOptional() // ignored by validation because set at DB level
-		@IsDate()
 		createdAt: Date;
 
-		@UpdateDateColumn({
-			...tsColumnOptions,
-			onUpdate: timestampSyntax,
-		})
-		@IsOptional() // ignored by validation because set at DB level
-		@IsDate()
+		@UpdateDateColumn(tsColumnOptions)
 		updatedAt: Date;
 
 		@BeforeUpdate()