feat: Postfach-Formular in den Einstellungen

Server, Port, Benutzer und Passwort eintragen, Verbindung testen, Ordner
danach aus der echten Liste des Postfachs waehlen. Je Absender wird ein
Zielkonto zugeordnet – ohne Zuordnung uebernimmt Certain nichts, denn
dieselbe Adresse kann je nach Konto etwas anderes bedeuten.

Der Hinweis am Passwortfeld sagt, was passiert, wenn das Server-Geheimnis
getauscht wird, und empfiehlt ein App-Passwort statt des echten.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/locales/en.json

@@ -493,5 +493,35 @@
     "viaShortcut": "via shortcut",
     "discard": "Discard",
     "discardConfirm": "Discard this capture? The booking is deleted. The entry stays marked as discarded so the statement still recognises the payment later."
+  },
+  "mailbox": {
+    "title": "Mailbox for payment emails",
+    "intro": "Raiffeisen and Revolut send an email for transfers. Certain fetches them and puts them into the inbox as suggestions – only what you approve gets booked. Card payments in a shop are not emailed by the banks; use the shortcut capture under “My account” for those.",
+    "add": "Add mailbox",
+    "name": "Label",
+    "namePlaceholder": "e.g. Receipts",
+    "host": "IMAP server",
+    "port": "Port",
+    "username": "Username",
+    "password": "Password",
+    "passwordKeep": "Password (leave empty to keep)",
+    "passwordHint": "Stored encrypted. The key derives from the server secret: if that is replaced, you must enter the password again. Prefer an app password over your real one.",
+    "folder": "Folder",
+    "folderHint": "After a connection test you can pick from the real folders here.",
+    "doneFolder": "Move to after processing",
+    "doneFolderPlaceholder": "empty = do not move",
+    "pollMinutes": "Fetch every … minutes",
+    "test": "Test connection",
+    "testOk": "Connection works – {{n}} folders found.",
+    "fetchNow": "Fetch now",
+    "fetched": "{{neu}} new, {{unklar}} unclear.",
+    "lastPoll": "last fetched",
+    "neverPolled": "never fetched",
+    "lastError": "Error",
+    "delete": "Remove mailbox",
+    "deleteConfirm": "Remove mailbox “{{name}}”? Payments already captured stay.",
+    "noSenders": "No sender mapped yet – without a mapping nothing is taken over.",
+    "noAccount": "no account",
+    "fromPlaceholder": "Sender contains, e.g. raiffeisen.ch"
   }
 }