fix(syslog): word its audit actions, list its tables for backups, mark its page top-level, reach its modules as loaded (#5999)

- Audit: syslog.source_* worded, and a Syslog filter area.
- Backups keep syslog_sources (added, named, ignored; what it last sent
  isn't compared) and leave syslog_lines out, as logs.
- The integration test reaches the plugin as loaded (#5775), so its
  tables aren't defined twice; ruff E741.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/plugins/syslog/test_syslog_page.py

@@ -56,7 +56,7 @@ async def test_a_viewer_sees_sources_but_no_controls(app):
 async def test_a_port_it_cannot_open_is_said(app):
     page = await _render(app, "admin", listener=_listener(
         listening=False, error="Port 514 couldn't be opened (UDP: Permission denied)."))
-    assert "Not listening" in page and "Port 514 couldn't be opened" in page
+    assert "Not listening" in page and "Port 514 couldn't be opened" in page
     assert "below 1024" in page
     assert "No sources yet." in page