Suppress two Bandit false positives in the new FTP and batch-order tests

The 1.2.5.3 code-scanning run flagged two new alerts, both in test files
added this release, and both false positives.

B402, the ftplib import in the #2780 connect-cleanup tests, is the HIGH
finding that failed the check. The test imports ftplib to construct the
exceptions BambuFTPClient.connect has to survive -- error_perm and
error_temp, at lines 50, 51 and 75. Nothing in the file opens a
connection, and bambu_ftp.py already carries the same marker on its own
import.

B108, the /tmp path in the batch-order archive fixture, is the MEDIUM
one. The value is a string written into PrintArchive.file_path so the
row has a path; nothing ever opens it. Every other archive fixture in
the suite carries the same marker on the same idiom.

Both markers follow the wording already in test_bambu_ftp.py and
test_sjf_scheduling.py. Bandit's medium+ count over backend/ drops from
17 to 15, and neither file contributes to what is left.

backend/tests/integration/test_print_batch_orders.py

@@ -49,7 +49,7 @@ async def archive_factory(db_session):
         defaults = {
             "filename": f"batch_order_{counter}.3mf",
             "print_name": f"Batch Order {counter}",
-            "file_path": f"/tmp/batch_order_{counter}.3mf",
+            "file_path": f"/tmp/batch_order_{counter}.3mf",  # nosec B108
             "file_size": 2048,
             "content_hash": f"batchhash{counter:08d}",
             "status": "completed",

backend/tests/unit/services/test_ftp_failed_connect_cleanup_2780.py

@@ -18,7 +18,7 @@ These tests assert the socket is closed, not merely dereferenced, because
 dereferencing is what the old code did and it looked identical from outside.
 """
 
-import ftplib
+import ftplib  # nosec B402 — tests need the real ftplib to construct its own error types
 import ssl
 from unittest.mock import MagicMock, patch