Fixes for 1.12 (#4655)

* fix missing locales
* bump composer packages
* changed translations
* assert timezone on customer
* include user accountNumber in excel export
* improve next customer number calculation
* fix z-index of contextmenu / action dropdown

src/Entity/Customer.php

@@ -146,6 +146,7 @@ class Customer implements EntityWithMetaFields, EntityWithBudget
      */
     #[ORM\Column(name: 'timezone', type: 'string', length: 64, nullable: false)]
     #[Assert\NotBlank]
+    #[Assert\Timezone]
     #[Assert\Length(max: 64)]
     #[Serializer\Expose]
     #[Serializer\Groups(['Customer_Entity'])]