Copy directly-sent e-mails to an IMAP Sent folder, with a live folder picker

A raw SMTP send has no server-side "Sent" copy on its own (unlike IMAP
drafts, which are inherently server-side) -- add an opt-in checkbox plus a
configurable target folder so directly sent Mahnungen/SEPA-info-mails still
show up in the account's Gesendet/Sent folder like a normal mail client
would leave them. Applies only to "send" delivery; drafts already live on
the server by definition.

Both the Entwürfe- and Gesendet-folder fields are now editable comboboxes:
a new "Ordnerliste laden" button fetches the real folder list from the IMAP
server (needs working credentials first) via LIST, decoding folder names
from modified UTF-7 (RFC 3501) so names like "Entwürfe" render correctly
instead of as "Entw&APw-rfe". Free text still works -- ensure_imap_folder()
creates the folder on first use if it doesn't exist yet, checked once per
batch rather than before every single message.

mail_delivery.append_to_imap_drafts() became the more general
append_message(client, content, folder=, flags=), reused for both the
\Draft and \Seen cases.

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

src/ccma/services/sepa_mail.py

@@ -10,7 +10,13 @@ from email.policy import SMTP
 from email.utils import format_datetime, make_msgid
 from pathlib import Path
 
-from ccma.services.mail_delivery import append_to_imap_drafts, imap_session, send_via_smtp, smtp_session
+from ccma.services.mail_delivery import (
+    append_message,
+    ensure_imap_folder,
+    imap_session,
+    send_via_smtp,
+    smtp_session,
+)
 from ccma.services.sepa import DirectDebit
 from ccma.storage.repository import MemberRepository, RepositoryError
 
@@ -105,18 +111,21 @@ def generate_debit_mails(
 ) -> tuple[list[GeneratedDebitMail], list[str]]:
     output: Path | None = None
     email_settings: dict | None = None
+    smtp_ctx = nullcontext(None)
+    imap_ctx = nullcontext(None)
     if delivery_mode == "local":
         if not output_directory:
             raise RepositoryError("Kein Zielordner für die lokale Ablage angegeben.")
         output = Path(output_directory)
         output.mkdir(parents=True, exist_ok=True)
-        session = nullcontext(None)
     elif delivery_mode == "send":
         email_settings = repository.get_email_settings()
-        session = smtp_session(email_settings)
+        smtp_ctx = smtp_session(email_settings)
+        if email_settings["imap_sent_enabled"]:
+            imap_ctx = imap_session(email_settings)
     elif delivery_mode == "drafts":
         email_settings = repository.get_email_settings()
-        session = imap_session(email_settings)
+        imap_ctx = imap_session(email_settings)
     else:
         raise RepositoryError(f"Unbekannter Versandmodus: {delivery_mode}")
 
@@ -126,9 +135,14 @@ def generate_debit_mails(
         raise RepositoryError("In den Optionen fehlt die Gläubiger-ID.")
     generated: list[GeneratedDebitMail] = []
     warnings: list[str] = []
-    # One connection is opened for the whole batch (a run can cover dozens of
-    # members) instead of reconnecting/re-authenticating per recipient.
-    with session as client:
+    # One connection (or two, for "send" with a Sent-folder copy) is opened for the
+    # whole batch -- a run can cover dozens of members -- instead of reconnecting/
+    # re-authenticating per recipient.
+    with smtp_ctx as smtp_client, imap_ctx as imap_client:
+        if delivery_mode == "drafts":
+            ensure_imap_folder(imap_client, email_settings["imap_drafts_folder"])
+        elif delivery_mode == "send" and imap_client is not None:
+            ensure_imap_folder(imap_client, email_settings["imap_sent_folder"])
         for debit in debits:
             member = repository.get_member(debit.member_id)
             if not member.email.strip():
@@ -156,9 +170,15 @@ def generate_debit_mails(
                 export_path = _available_path(output, filename)
                 export_path.write_bytes(content)
             elif delivery_mode == "send":
-                send_via_smtp(client, content)
+                send_via_smtp(smtp_client, content)
+                if imap_client is not None:
+                    append_message(
+                        imap_client, content, folder=email_settings["imap_sent_folder"], flags=r"(\Seen)"
+                    )
             else:
-                append_to_imap_drafts(client, content, folder=email_settings["imap_drafts_folder"])
+                append_message(
+                    imap_client, content, folder=email_settings["imap_drafts_folder"], flags=r"(\Draft)"
+                )
             try:
                 archive_path.write_bytes(content)
             except OSError: