feat(web): merge Fleet into a server-filterable Dashboard

Implements Phase 1 of the UI navigation rework (docs/superpowers/specs/
2026-06-02-ui-navigation-rework.md): the Dashboard now lists every workspace
across every configured server as <workspace> (<server>), filterable by server,
with cross-server aggregate cards (reusing computeFleetAggregates). Opening a
workspace activates its server then drills into the existing detail route.
Per-server fan-out lives in a ServerWorkspaceRows child (rules-of-hooks safe,
mirrors FleetRow). Fleet removed from the sidebar nav; the /fleet route is left
intact for now (full removal deferred to avoid churning fleet.test.tsx while #54
is open).

packages/web/src/components/layout/Sidebar.tsx

@@ -15,7 +15,6 @@ import {
 	MessageSquare,
 	Moon,
 	MoonStar,
-	Network,
 	Settings,
 	Sun,
 	Users,
@@ -32,7 +31,6 @@ import { COLOR } from "@/lib/constants";
 
 const TOP_NAV = [
 	{ to: "/" as const, label: "Dashboard", icon: LayoutDashboard, exact: true },
-	{ to: "/fleet" as const, label: "Fleet", icon: Network, exact: false },
 	{ to: "/workspaces" as const, label: "Workspaces", icon: Boxes, exact: false },
 	{ to: "/seed-kits" as const, label: "Seed Kits", icon: Layers, exact: false },
 	{ to: "/settings" as const, label: "Settings", icon: Settings, exact: false },