Add ensure_jail_configs startup check for required jail config files

On startup BanGUI now verifies that the four fail2ban jail config files
required by its two custom jails (manual-Jail and blocklist-import) are
present in `$fail2ban_config_dir/jail.d`.  Any missing file is created
with the correct default content; existing files are never overwritten.

Files managed:
  - manual-Jail.conf        (enabled=false template)
  - manual-Jail.local       (enabled=true override)
  - blocklist-import.conf   (enabled=false template)
  - blocklist-import.local  (enabled=true override)

The check runs in the lifespan hook immediately after logging is
configured, before the database is opened.

backend/tests/test_routers/test_setup.py

@@ -330,6 +330,7 @@ class TestLifespanDatabaseDirectoryCreation:
             patch("app.tasks.geo_cache_flush.register"),
             patch("app.tasks.geo_re_resolve.register"),
             patch("app.main.AsyncIOScheduler", return_value=mock_scheduler),
+            patch("app.main.ensure_jail_configs"),
         ):
             async with _lifespan(app):
                 assert nested_db.parent.exists(), (
@@ -372,6 +373,7 @@ class TestLifespanDatabaseDirectoryCreation:
             patch("app.tasks.geo_cache_flush.register"),
             patch("app.tasks.geo_re_resolve.register"),
             patch("app.main.AsyncIOScheduler", return_value=mock_scheduler),
+            patch("app.main.ensure_jail_configs"),
         ):
             # Should not raise FileExistsError or similar.
             async with _lifespan(app):