feat: mail attachment support — sync, display, download, upload

frontend/src/i18n/locales/de.json

@@ -41,6 +41,7 @@
   "common": {
     "save": "Speichern",
     "cancel": "Abbrechen",
+    "remove": "Entfernen",
     "delete": "Löschen",
     "edit": "Bearbeiten",
     "create": "Erstellen",
@@ -427,6 +428,7 @@
     "subjectPlaceholder": "Betrereff eingeben...",
     "body": "Text",
     "attachments": "Anhänge",
+    "addAttachment": "Anhang hinzufügen",
     "download": "Herunterladen",
     "compose": "Verfassen",
     "send": "Senden",

frontend/src/i18n/locales/en.json

@@ -41,6 +41,7 @@
   "common": {
     "save": "Save",
     "cancel": "Cancel",
+    "remove": "Remove",
     "delete": "Delete",
     "edit": "Edit",
     "create": "Create",
@@ -427,6 +428,7 @@
     "subjectPlaceholder": "Enter subject...",
     "body": "Body",
     "attachments": "Attachments",
+    "addAttachment": "Add Attachment",
     "download": "Download",
     "compose": "Compose",
     "send": "Send",