chore(dashboard): remove orphaned /adapter-config route

AdapterConfig is already embedded directly in Environment.tsx
(excludeKeys={CURATED_KEYS} hideLlmToggle); no in-app <Link> ever
targeted the standalone /adapter-config route. Drop the route, its
App.tsx import, the extraTitleItems entry in Layout.tsx, and the
now-unused Sliders icon import. pages/AdapterConfig.tsx itself is
kept — it's imported directly by Environment.tsx.

work/dashboard-frontend/src/App.tsx

@@ -7,7 +7,6 @@ import Config from './pages/Config'
 import ActivityLog from './pages/ActivityLog'
 import Notifications from './pages/Notifications'
 import Reference from './pages/Reference'
-import AdapterConfig from './pages/AdapterConfig'
 import GaugeSites from './pages/GaugeSites'
 import TownAnchors from './pages/TownAnchors'
 import MeshCoreRouting from './pages/MeshCoreRouting'
@@ -41,7 +40,6 @@ function App() {
           {/* Legacy /notifications -> Meshtastic Routing */}
           <Route path="/notifications" element={<Navigate to="/meshtastic/routing" replace />} />
           <Route path="/reference" element={<Reference />} />
-          <Route path="/adapter-config" element={<AdapterConfig />} />
 
           {/* New aggregated pages */}
           <Route path="/places" element={<Places />} />

work/dashboard-frontend/src/components/Layout.tsx

@@ -7,7 +7,6 @@ import {
   Cloud,
   BellRing,
   BookOpen,
-  Sliders,
   Droplets,
   MapPin,
   Map,
@@ -86,7 +85,6 @@ const navGroups: NavGroup[] = [
 // Flattened view of every nav item for title lookup.
 // Also include de-navved routes so they still resolve a title.
 const extraTitleItems: NavItem[] = [
-  { path: '/adapter-config', label: 'Adapter Config', icon: Sliders },
   { path: '/gauge-sites', label: 'Gauge Sites', icon: Droplets },
   { path: '/town-anchors', label: 'Town Anchors', icon: MapPin },
   { path: '/mesh', label: 'Mesh', icon: Radio },