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/fail2ban_client.py

@@ -17,7 +17,6 @@ Usage::
 from __future__ import annotations
 
 import asyncio
-import contextlib
 import errno
 import sys
 import time
@@ -189,8 +188,15 @@ def _send_command_sync(
             ) from exc
         finally:
             if client is not None:
-                with contextlib.suppress(Exception):
+                try:
                     client.close()
+                except Exception as e:
+                    log.warning(
+                        "fail2ban_socket_close_error",
+                        socket_path=socket_path,
+                        error=str(e),
+                        exc_info=True,
+                    )
 
     raise Fail2BanConnectionError(
         str(last_oserror), socket_path