fix(prometheus, syslog): a target or pattern pauses with a Pause/Resume button, not an "on" tick box in its form (#6419)

Monitors, schedules and maintenance plans already pause with a
Pause/Resume button and say "Paused" where they're listed. Prometheus
targets and syslog patterns only had a tick box inside the edit form,
so a target refused by its endpoint couldn't be stopped from its page.

- Both get a Pause/Resume button (target page and list; patterns list)
  posting to /toggle, recorded in the audit log, and a Paused badge.
- The forms lose the tick box. A new one starts running; an edit keeps
  whether it is paused.
- A target's "off" state is now "paused", in its pages and MCP tools.
  A resumed target reads "not scraped yet" until its next scrape, and its
  counter rates start over.

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

tests/plugins/prometheus/test_mcp_tools.py

@@ -22,7 +22,7 @@ def _target(name, *, enabled=True, scraped=timedelta(seconds=30), error=None,
 def test_only_a_target_whose_scrape_failed_is_an_overview_finding():
     views = [t._target_view(x, {}, NOW) | {"_ok_at": x.last_ok_at} for x in (
         _target("archives", error="connection refused"), _target("fine"),
-        _target("off", enabled=False, error="connection refused"),
+        _target("paused", enabled=False, error="connection refused"),
         _target("stale", scraped=timedelta(days=1), error="connection refused"),
         _target("new", scraped=None))]
     [f] = t.target_findings(views)