feat(widgets): Routers and Hosts problem rows say since when (#5810)

Routers: a router in trouble reads 'started 2h ago' or 'all of the last
24 h', from problem_since over the day's history, read for the troubled
routers only (a certificate's problem carries its own date). Hosts: a
down host reads 'a monitor is down for 3h'; host_glance keeps the
down_since host_status already had.

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

tests/plugins/traefik/test_traefik_page.py

@@ -209,6 +209,21 @@ async def test_the_widget_gives_a_verdict_then_routers_under_one_header(app):
     assert "+4 more healthy" in page
 
 
+async def test_a_router_in_trouble_says_since_when_on_the_widget(app):
+    """#5810: the widget's problem rows carry the since the page shows."""
+    slow = _router("api@docker", _latest(p95=450.0))
+    slow.update(since=datetime.now(timezone.utc) - timedelta(hours=2), since_before=False)
+    failing = _router("pay@docker", _latest(e5=4.0))
+    failing.update(since=datetime.now(timezone.utc) - timedelta(days=1), since_before=True)
+    async with app.test_request_context("/plugins/traefik/widget"):
+        page = await render_plugin_template(
+            app, "traefik", "traefik/widget.html", problems=[failing, slow], healthy=[],
+            healthy_more=0, total=2, loose_certs=[], domains_known=True)
+    page = " ".join(page.split())
+    assert "all of the last 24 h" in page
+    assert page.count(", started ") == 1 and page.index("all of the last 24 h") < page.index(", started ")
+
+
 async def test_without_router_domains_expiring_certs_follow_the_routers(app):
     fine = _router("web@docker", _latest())
     async with app.test_request_context("/plugins/traefik/widget"):