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/test_breadcrumbs.py

@@ -24,6 +24,7 @@ TOP_LEVEL = {
     "plugins/prometheus/templates/prometheus/index.html",
     "plugins/traefik/templates/traefik/index.html",
     "plugins/unifi/templates/unifi/index.html",
+    "plugins/syslog/templates/syslog/index.html",
     # Logged out, or no page to go back up from.
     "steward/templates/auth/login.html",
     "steward/templates/auth/setup.html",