Add configurable e-mail delivery: direct SMTP send or IMAP drafts

Mahnungs- and SEPA-info-mails could previously only be saved as a local .eml
file that still had to be manually imported into Thunderbird. Add a per-store
"E-Mail-Versand" configuration (Optionen -> E-Mail-Versand, stored in
repository.json alongside the rest of the club's settings, since different
stores may use different mailboxes) with four delivery modes:

- "Lokal speichern": today's behaviour, unchanged default for existing stores.
- "Direkt versenden": sends via SMTP.
- "Als Entwurf ablegen": IMAP APPENDs into a configurable drafts folder, so it
  shows up live in whatever mail client is already watching that account.
- "Jedes Mal fragen": prompts once per generation action (not per e-mail --
  a SEPA batch can cover dozens of members) with Senden/Entwürfe/Abbrechen.

New ccma.services.mail_delivery module (smtplib/imaplib, no new dependency)
opens one authenticated connection per batch and reuses it across all
messages instead of reconnecting per recipient. Both "Verbindung testen"
buttons in Options exercise the same connection path used for real delivery.
The archived per-member copy of every generated e-mail is unaffected and
still always written regardless of delivery mode.

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

src/ccma/ui/claim_tab.py

@@ -25,6 +25,7 @@ from ccma.domain.dates import date_input_hint, format_date_for_display
 from ccma.services.reminder_mail import generate_and_send_reminder_mail
 from ccma.storage.repository import MemberRepository, RepositoryError
 from ccma.ui.document_dialog import DocumentTemplateDialog
+from ccma.ui.email_delivery_dialog import resolve_delivery_mode
 from ccma.ui.labels import (
     CLAIM_ITEM_TYPE_LABELS,
     REMINDER_CHANNEL_LABELS,
@@ -1258,22 +1259,29 @@ class ReminderMailDialog(tk.Toplevel):
         self.grab_set()
 
     def _generate(self) -> None:
-        selected = filedialog.asksaveasfilename(
-            parent=self,
-            title="Mahnung als Thunderbird-Entwurf speichern",
-            defaultextension=".eml",
-            initialfile=f"{self.reminder_name}.eml",
-            filetypes=[("E-Mail-Datei", "*.eml"), ("Alle Dateien", "*.*")],
-        )
-        if not selected:
+        delivery_mode = resolve_delivery_mode(self, self.repository)
+        if delivery_mode is None:
             return
+        output_path = None
+        if delivery_mode == "local":
+            selected = filedialog.asksaveasfilename(
+                parent=self,
+                title="Mahnung als Thunderbird-Entwurf speichern",
+                defaultextension=".eml",
+                initialfile=f"{self.reminder_name}.eml",
+                filetypes=[("E-Mail-Datei", "*.eml"), ("Alle Dateien", "*.*")],
+            )
+            if not selected:
+                return
+            output_path = selected
         try:
             result = generate_and_send_reminder_mail(
                 self.repository,
                 self.member_id,
                 self.claim_id,
                 self.reminder_id,
-                output_path=selected,
+                delivery_mode=delivery_mode,
+                output_path=output_path,
                 sender_name=self.sender_name_var.get(),
                 sender_email=self.sender_email_var.get(),
                 signature=self.signature.get("1.0", "end-1c"),
@@ -1281,9 +1289,14 @@ class ReminderMailDialog(tk.Toplevel):
         except (OSError, RepositoryError) as exc:
             messagebox.showerror("Mahnung konnte nicht erzeugt werden", str(exc), parent=self)
             return
+        outcome = {
+            "local": f"gespeichert:\n{result.export_path}",
+            "send": "direkt versandt.",
+            "drafts": "als Entwurf im Postfach abgelegt.",
+        }[delivery_mode]
         messagebox.showinfo(
             "Mahnung erzeugt",
-            f"Die E-Mail wurde gespeichert und als versandt gebucht:\n{result.export_path}",
+            f"Die E-Mail wurde {outcome}\n\nDie Mahnung wurde als versandt gebucht.",
             parent=self,
         )
         self.destroy()