feat(dashboard): merge top summary strip + Status widget into one Overview

Operator chose a single canonical summary. Repurpose the status_overview
widget into 'Overview' (host count + monitor up/down/pending + Alerts link;
key kept so existing dashboards upgrade in place) and remove the redundant
fixed top strip from the dashboard view. Drops _get_summary_stats and its
now-unused PingResult/DnsResult imports (rule 22).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

steward/dashboard/routes.py

@@ -9,7 +9,6 @@ from sqlalchemy import select, func, update
 from steward.auth.middleware import require_role, current_user_id
 from steward.models.users import UserRole
 from steward.models.hosts import Host
-from steward.models.monitors import PingResult, DnsResult
 from steward.models.dashboard import Dashboard, DashboardWidget, DashboardShareToken
 from steward.core.settings import public_base_url
 from steward.core.widgets import get_available_widgets, WIDGET_REGISTRY
@@ -103,42 +102,6 @@ async def _get_or_create_system_default(db) -> Dashboard:
     return dash
 
 
-async def _get_summary_stats(db) -> dict:
-    latest_ping_subq = (
-        select(PingResult.host_id, func.max(PingResult.probed_at).label("max_at"))
-        .group_by(PingResult.host_id).subquery()
-    )
-    pr = await db.execute(
-        select(PingResult).join(
-            latest_ping_subq,
-            (PingResult.host_id == latest_ping_subq.c.host_id)
-            & (PingResult.probed_at == latest_ping_subq.c.max_at),
-        )
-    )
-    pings     = list(pr.scalars())
-    ping_up   = sum(1 for p in pings if p.status.value == "up")
-    ping_down = sum(1 for p in pings if p.status.value == "down")
-
-    latest_dns_subq = (
-        select(DnsResult.host_id, func.max(DnsResult.resolved_at).label("max_at"))
-        .group_by(DnsResult.host_id).subquery()
-    )
-    dr = await db.execute(
-        select(DnsResult).join(
-            latest_dns_subq,
-            (DnsResult.host_id == latest_dns_subq.c.host_id)
-            & (DnsResult.resolved_at == latest_dns_subq.c.max_at),
-        )
-    )
-    dns      = list(dr.scalars())
-    dns_ok   = sum(1 for d in dns if d.status.value == "resolved")
-    dns_fail = sum(1 for d in dns if d.status.value != "resolved")
-    total    = (await db.execute(select(func.count()).select_from(Host))).scalar()
-
-    return dict(ping_up=ping_up, ping_down=ping_down,
-                dns_ok=dns_ok, dns_fail=dns_fail, total_hosts=total)
-
-
 def _resolve_widgets(widgets: list[DashboardWidget]) -> list[dict]:
     plugins_cfg = current_app.config.get("PLUGINS", {})
     out = []
@@ -199,7 +162,6 @@ async def view(dash_id: int):
         if dash is None or not _can_view(dash, user_id, user_role):
             abort(404)
 
-        stats      = await _get_summary_stats(db)
         widgets    = await _get_widgets(db, dash_id)
         accessible = await _accessible_dashboards(db, user_id, user_role)
         can_edit   = _can_edit(dash, user_id, user_role)
@@ -224,7 +186,6 @@ async def view(dash_id: int):
         can_edit=can_edit,
         addable=addable,
         hosts=hosts,
-        **stats,
     )