fix: handle socket close errors properly in PapertrailLogHandler

- Replace contextlib.suppress with try/except + warning log
- Add test for fail2ban client
- Remove stale Issue #21 from Tasks.md (indexes)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/app/utils/external_logging.py

@@ -7,7 +7,6 @@ fashion using async buffering and batching.
 from __future__ import annotations
 
 import asyncio
-import contextlib
 import json
 from abc import ABC, abstractmethod
 from collections import deque
@@ -244,8 +243,10 @@ class PapertrailLogHandler(ExternalLogHandler):
                 await writer.drain()
         finally:
             writer.close()
-            with contextlib.suppress(Exception):
+            try:
                 await writer.wait_closed()
+            except Exception as e:
+                log.warning("external_logging_writer_close_error", error=str(e))
 
     @staticmethod
     def _severity_from_level(level: str) -> int: