Enhancement: add processed mails management UI and API

src-ui/src/app/data/processed-mail.ts

@@ -0,0 +1,12 @@
+import { ObjectWithId } from './object-with-id'
+
+export interface ProcessedMail extends ObjectWithId {
+  rule: number // MailRule.id
+  folder: string
+  uid: number
+  subject: string
+  received: Date
+  processed: Date
+  status: string
+  error: string
+}