fix(traefik): the rows page reads every router's history in one index-only query (#5355)

#5355 "Traefik page doesn't load": /plugins/traefik/rows took 12-28 s.
It ran a query per router ever seen, and each raw row in the range was a
heap fetch. traefik_004 rebuilds the router index to cover the charted
columns and indexes scraped_at for the request chart; router_history reads
the current routers' buckets in one query.

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

tests/integration/test_traefik_latest.py

@@ -74,3 +74,37 @@ def test_the_request_chart_sums_routers_and_weights_the_5xx_share(app):
     got = asyncio.run(go())
     # One bucket: totals 4 and 6 average to 5; 150 weighted 5xx over 10 req/s is 15%.
     assert got == [{"at": at, "req_rate": 5.0, "err_pct": 15.0}]
+
+
+def test_router_history_reads_every_router_in_one_query_bucketed(app):
+    """#5214: the rows page read each router's history in its own query, a
+    heap fetch per row, and took 12-28 s. One query now buckets every named
+    router; a router not asked for is not read, and one with no rows in the
+    range still has an (empty) entry."""
+    from plugins.traefik.models import TraefikMetric
+    from plugins.traefik.routes import router_history
+
+    at = datetime(2098, 6, 1, 12, 0, tzinfo=timezone.utc) + timedelta(minutes=5 * (uuid.uuid4().int % 2_000))
+    tag = uuid.uuid4().hex[:8]
+    a, b, c, idle = (f"{x}-{tag}@docker" for x in ("a", "b", "c", "idle"))
+
+    def row(name, minute, rate, p95=2.0):
+        return TraefikMetric(router_name=name, scraped_at=at + timedelta(minutes=minute), request_rate=rate,
+                             error_rate_4xx_pct=0.0, error_rate_5xx_pct=0.0, latency_p50_ms=1.0,
+                             latency_p95_ms=p95, latency_p99_ms=3.0, response_bytes_rate=0.0)
+
+    async def go():
+        async with app.db_sessionmaker() as s:
+            async with s.begin():
+                s.add_all([row(a, 0, 1.0, 10.0), row(a, 1, 3.0, 30.0), row(a, 5, 7.0),
+                           row(b, 0, 4.0), row(c, 0, 9.0), row(idle, -60, 5.0)])
+            async with s.begin():
+                return await router_history(s, [a, b, idle], at, 300)
+
+    got = asyncio.run(go())
+    assert set(got) == {a, b, idle}                                   # c was not asked for
+    # a: minutes 0 and 1 share the first 5-minute bucket and average; minute 5 starts the next.
+    assert [r.request_rate for r in got[a]] == [2.0, 7.0]
+    assert got[a][0].latency_p95_ms == 20.0
+    assert [r.request_rate for r in got[b]] == [4.0]
+    assert got[idle] == []                                            # its only row is before the range