feat(dashboard): a curated default layout, merged duplicate widgets, a labelled Overview (#5213)

- New installs start from widgets.RECOMMENDED, packed row by row for the
  enabled plugins; the edit drawer can reset a dashboard to it.
- Host Agent — Resources folds into Hosts — Overview (which gains load 1m),
  UniFi — Devices into UniFi — Overview; migration 0032 moves existing
  dashboards onto the survivors.
- The Overview labels what it counts (hosts, monitors up/down/pending,
  alerts firing) and lists firing alerts and down monitors with since-times.
- Uptime polls every 5 minutes (poll_seconds) instead of every cycle.

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

plugins/host_agent/routes.py

@@ -17,7 +17,7 @@ from sqlalchemy import select, or_, and_
 from datetime import timedelta
 
 from steward.core.formatting import worst_reading
-from steward.core.metric_series import latest_by_resource, points as metric_points
+from steward.core.metric_series import points as metric_points
 from steward.core.settings import get_setting, public_base_url
 from steward.core.time_range import parse_range, RANGE_OPTIONS
 from steward.models.hosts import Host
@@ -477,108 +477,6 @@ def _stale_after_seconds() -> int:
     )
 
 
-async def _fleet_rows(session) -> list[dict]:
-    """One row per registered host with its latest host-level metrics + stale flag.
-
-    Only bare host-level resources are used here (sub-resources carry a ':' and
-    are skipped) so the fleet glance stays one line per host.
-    """
-    regs = (await session.execute(select(HostAgentRegistration))).scalars().all()
-    host_ids = [r.host_id for r in regs]
-    hosts = {
-        h.id: h for h in (await session.execute(
-            select(Host).where(Host.id.in_(host_ids))
-        )).scalars().all()
-    } if host_ids else {}
-
-    host_names = [h.name for h in hosts.values()]
-    latest_by = await latest_by_resource(
-        session, SOURCE_MODULE, host_names + [n + ":/" for n in host_names])
-    latest: dict[str, dict[str, float]] = {}
-    root_disk: dict[str, float] = {}  # host_name → root (/) disk %
-    for resource, metrics in latest_by.items():
-        if resource.endswith(":/"):
-            if "disk_used_pct" in metrics:
-                root_disk[resource[:-2]] = metrics["disk_used_pct"].value
-            continue
-        latest[resource] = {m: r.value for m, r in metrics.items()}
-
-    # Per-host recent series for the inline sparklines (cpu/mem/load host-level,
-    # disk from the root mount), so each metric shows its trend beside the value —
-    # the host-panel at-a-glance, on the fleet widget. 1h window keeps it cheap.
-    spark_series: dict[str, dict[str, list]] = {
-        n: {"cpu": [], "mem": [], "disk": [], "load": []} for n in host_names
-    }
-    if host_names:
-        since = datetime.now(timezone.utc) - timedelta(hours=1)
-        sp_rows = (await session.execute(
-            select(PluginMetric).where(
-                PluginMetric.source_module == SOURCE_MODULE,
-                PluginMetric.recorded_at >= since,
-                or_(
-                    and_(PluginMetric.resource_name.in_(host_names),
-                         PluginMetric.metric_name.in_(("cpu_pct", "mem_used_pct", "load_1m"))),
-                    and_(PluginMetric.resource_name.in_([n + ":/" for n in host_names]),
-                         PluginMetric.metric_name == "disk_used_pct"),
-                ),
-            ).order_by(PluginMetric.recorded_at)
-        )).scalars().all()
-        for r in sp_rows:
-            if r.resource_name.endswith(":/"):
-                name = r.resource_name[:-2]
-                if name in spark_series:
-                    spark_series[name]["disk"].append(r.value)
-            else:
-                key = {"cpu_pct": "cpu", "mem_used_pct": "mem", "load_1m": "load"}.get(r.metric_name)
-                if key and r.resource_name in spark_series:
-                    spark_series[r.resource_name][key].append(r.value)
-
-    from steward.core.status import sparkline_svg
-
-    stale_after = _stale_after_seconds()
-    now = datetime.now(timezone.utc)
-    rows = []
-    for reg in regs:
-        host = hosts.get(reg.host_id)
-        if host is None:
-            continue
-        m = latest.get(host.name, {})
-        ls = reg.last_seen_at
-        stale = ls is None or (now - ls).total_seconds() > stale_after
-        ser = spark_series.get(host.name, {})
-        sparks = {
-            k: (sparkline_svg(v[-60:], width=72, height=16) if len(v) >= 2 else "")
-            for k, v in ser.items()
-        }
-        rows.append({
-            "host": host,
-            "reg": reg,
-            "stale": stale,
-            "cpu_pct": m.get("cpu_pct"),
-            "mem_used_pct": m.get("mem_used_pct"),
-            "disk_worst": m.get("disk_used_pct_worst"),  # health dot only
-            "disk_root": root_disk.get(host.name),       # displayed at-a-glance
-            "load_1m": m.get("load_1m"),
-            "temp_max": m.get("temp_c_max"),
-            "net_rx_bps": m.get("net_rx_bps"),
-            "net_tx_bps": m.get("net_tx_bps"),
-            "disk_read_bps": m.get("disk_read_bps"),
-            "disk_write_bps": m.get("disk_write_bps"),
-            "sparks": sparks,
-        })
-    rows.sort(key=lambda r: r["host"].name.lower())
-    return rows
-
-
-@host_agent_bp.get("/widget")
-@require_role(UserRole.viewer)
-async def widget_table():
-    """Fleet-glance dashboard widget: one row per monitored host, latest metrics."""
-    async with current_app.db_sessionmaker() as session:
-        rows = await _fleet_rows(session)
-    return await render_template("widget_table.html", rows=rows)
-
-
 @host_agent_bp.get("/widget/history")
 @require_role(UserRole.viewer)
 async def widget_history():