feat(docker): Busiest Containers shows bars of the last hours beside each figure, scaled to the row's peak with a floor (#5214)

The fill bars were a share of the host's capacity, a sliver on hosts with
80 cores. Each figure now sits beside 24 bars of the last 6 hours (1h/24h
per widget), each row scaled to its own peak but never below 1 core or
1 GiB (configurable per widget), so a 0.05-core container reads flat and
a bar's height means real load. One grouped date_bin query feeds them.

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

tests/integration/test_docker_recent_usage.py

@@ -0,0 +1,49 @@
+"""Integration: Busiest Containers bars average each container's samples per
+time bucket in one query (#5214). Two samples share a bucket and must merge
+(lesson #5262). Requires STEWARD_DATABASE_URL."""
+from __future__ import annotations
+
+import asyncio
+import os
+import uuid
+from datetime import datetime, timedelta, timezone
+
+import pytest
+
+pytestmark = pytest.mark.integration
+
+
+@pytest.fixture
+def app():
+    if not os.environ.get("STEWARD_DATABASE_URL"):
+        pytest.skip("needs Postgres")
+    from steward.app import create_app
+    return create_app(testing=False)
+
+
+def test_recent_usage_averages_each_containers_bucket(app):
+    from plugins.docker.models import DockerMetric
+    from plugins.docker.service import bar_slots, recent_usage
+    from steward.models.hosts import Host
+
+    tag = uuid.uuid4().hex[:8]
+    hid = str(uuid.uuid4())
+    slots, width = bar_slots(datetime.now(timezone.utc), 6)
+    at = slots[-2]                                   # a whole bucket, in the past
+
+    def m(name, secs, cpu, mem):
+        return DockerMetric(host_id=hid, container_name=name, scraped_at=at + timedelta(seconds=secs),
+                            cpu_pct=cpu, mem_pct=0.0, mem_usage_bytes=mem)
+
+    async def go():
+        async with app.db_sessionmaker() as s:
+            async with s.begin():
+                s.add(Host(id=hid, name=f"dock-{tag}", address="10.9.9.4"))
+            async with s.begin():
+                s.add_all([m(f"a-{tag}", 10, 100.0, 1000), m(f"a-{tag}", 70, 300.0, 3000),
+                           m(f"b-{tag}", 10, 50.0, 500)])
+            async with s.begin():
+                return await recent_usage(s, {(hid, f"a-{tag}")}, slots[0], width)
+
+    got = asyncio.run(go())
+    assert got == {(hid, f"a-{tag}"): {at: (200.0, 2000.0)}}