Cover archive-directory setup in the sent/delivered rollback path

archive_dir.mkdir() and the archive path lookup ran outside the
try/except that decides whether to revert mark_reminder_sent (reminder
mail) or keep a SEPA batch running for the other debits. A failure there
(read-only store, full disk) left a reminder booked as "sent" with no
mail ever having gone out, and could still abort an entire SEPA batch
for one member's directory problem.

Moved that setup inside the same try blocks so it's treated exactly like
any other pre-delivery failure: reminder_mail reverts to draft, and
sepa_mail records a warning and continues with the remaining debits.
Also moved debit_mail_bytes() into the per-debit try in sepa_mail for
the same reason. Added a targeted mkdir-failure test for each.

src/ccma/services/sepa_mail.py

@@ -148,24 +148,8 @@ def generate_debit_mails(
             if not member.email.strip():
                 warnings.append(f"{member.member_number or member.display_name}: E-Mail-Adresse fehlt.")
                 continue
-            content = debit_mail_bytes(
-                recipient=member.email,
-                first_name=member.first_name,
-                debit=debit,
-                collection_date=collection_date,
-                creditor_id=creditor_id,
-                sender_name=sender_name,
-                sender_email=sender_email,
-                signature=signature,
-            )
-            filename = (
-                f"SEPA-Info-{collection_date.isoformat()}-"
-                f"{_safe_filename(member.member_number or member.display_name)}.eml"
-            )
-            archive_dir = repository.members_root / member.member_id / "files" / "documents" / "SEPA"
-            archive_dir.mkdir(parents=True, exist_ok=True)
-            archive_path = _available_path(archive_dir, filename)
             export_path: Path | None = None
+            archive_path: Path | None = None
             # Once the mail has actually left the building for this debit -- SMTP
             # accepted it, it's filed in the IMAP folder, or the local export file was
             # written -- a later archiving failure must not abort the whole batch and
@@ -174,6 +158,25 @@ def generate_debit_mails(
             delivered = False
             archive_failure: Exception | None = None
             try:
+                content = debit_mail_bytes(
+                    recipient=member.email,
+                    first_name=member.first_name,
+                    debit=debit,
+                    collection_date=collection_date,
+                    creditor_id=creditor_id,
+                    sender_name=sender_name,
+                    sender_email=sender_email,
+                    signature=signature,
+                )
+                filename = (
+                    f"SEPA-Info-{collection_date.isoformat()}-"
+                    f"{_safe_filename(member.member_number or member.display_name)}.eml"
+                )
+                archive_dir = (
+                    repository.members_root / member.member_id / "files" / "documents" / "SEPA"
+                )
+                archive_dir.mkdir(parents=True, exist_ok=True)
+                archive_path = _available_path(archive_dir, filename)
                 if delivery_mode == "local":
                     export_path = _available_path(output, filename)
                     export_path.write_bytes(content)