feat: unified rail shell, robust live sync, task board performance

Shell:
- One shared NexusLayout for ALL routes (dashboard + pages): compact 68px
  icon rail with hover-expand overlay, replaces both old sidebars + topbars
- Single flat nav source (railNav) — same menu everywhere incl. Settings
- Removed dead shell components (AppSidebar, AppHeader, Topbar, NavGroup,
  NavItem, ModuleView) and dead nav routes; App.vue is now just RouterView

Live updates:
- Fix SSE loop in DashboardController: PeriodicTimer.WaitForNextTickAsync and
  ChannelReader.ReadAsync were re-invoked while pending — every published
  update threw InvalidOperationException and killed ALL live streams
- liveSync store: treat graceful stream close as disconnect (was stuck
  connected=true with polling stopped -> page frozen until manual reload),
  fast first retry, heartbeat watchdog (65s), reconnect on online/visibility
- One app-wide SSE connection owned by the layout instead of per-view
  connect/disconnect churn; removed duplicate live-sync.ts store

Performance:
- Board endpoint: drop nested childTasks duplication (counts stay) — payload
  104KB -> 65KB; SSE snapshots shrink equally
- nginx: gzip for JSON/JS/CSS (board 18KB, bundle 95KB over the wire);
  text/event-stream excluded to keep SSE unbuffered

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/App.vue

@@ -1,156 +1,14 @@
 <script setup lang="ts">
-import { computed, onMounted, ref } from 'vue'
-import { Activity } from '@lucide/vue'
-import { RouterView, useRoute, useRouter } from 'vue-router'
-import { useOperationsStore } from './stores/operations'
-import { useAuthStore } from './stores/auth'
-import AppSidebar from './components/layout/AppSidebar.vue'
-import AppHeader from './components/layout/AppHeader.vue'
-import GalaxyBackground from './components/background/GalaxyBackground.vue'
-import ModuleView from './components/ModuleView.vue'
+/**
+ * App — nur noch Router-Einstieg + Toasts.
+ * Die Shell (Rail, Hintergrund, Live-Sync) lebt in layouts/NexusLayout.vue
+ * und umschließt alle Seiten außer dem Login.
+ */
+import { RouterView } from 'vue-router'
 import ToastContainer from './components/ui/ToastContainer.vue'
-
-const store = useOperationsStore()
-const auth = useAuthStore()
-const route = useRoute()
-const router = useRouter()
-
-const activeView = computed(() => {
-  if (route.name === 'Settings') return 'Settings'
-  if (route.name === 'ProjectDetail') return 'ProjectDetail'
-  return String(route.name ?? 'Dashboard')
-})
-
-const routePaths: Record<string, string> = {
-  Dashboard: '/dashboard', Memory: '/memory', Docs: '/docs', Security: '/security',
-  Projects: '/projects', 'Task Board': '/tasks', Incidents: '/incidents', Calendar: '/calendar',
-  Agents: '/agents', Models: '/models', Activity: '/activity', 'Mobile Chat': '/chat', Notifications: '/notifications', Settings: '/settings',
-}
-
-const navigate = (label: string) => {
-  mobileNavOpen.value = false
-  return router.push(routePaths[label] ?? '/dashboard')
-}
-const mobileNavOpen = ref(false)
-
-const standaloneViews = computed(() => {
-  if (route.name === 'Dashboard') return true
-  if (route.meta?.standalone) return true
-  return false
-})
-
-onMounted(() => {
-  if (auth.isAuthenticated) store.refresh()
-})
 </script>
 
 <template>
-  <RouterView v-if="route.name === 'Login' || route.name === 'Dashboard'" />
-  <div v-else class="shell">
-    <GalaxyBackground />
-    <AppSidebar
-      :active-view="activeView"
-      :mobile-nav-open="mobileNavOpen"
-      :queued-tasks="store.snapshot.metrics.queuedTasks"
-      :incidents="store.snapshot.metrics.incidents"
-      @navigate="navigate"
-    />
-
-    <main>
-      <AppHeader
-        :connected="store.connected"
-        @toggle-mobile-nav="mobileNavOpen = !mobileNavOpen"
-      />
-
-      <section class="content">
-        <RouterView v-if="standaloneViews" />
-
-        <template v-else>
-          <div class="page-heading">
-            <div>
-              <span class="eyebrow">MISSION CONTROL</span>
-              <h1>{{ activeView }}</h1>
-              <p>System overview and operational intelligence across Noveria.</p>
-            </div>
-            <button class="refresh" @click="store.refresh()">
-              <Activity :size="15" :class="{ spin: store.loading }" />
-              Refresh
-            </button>
-          </div>
-
-          <ModuleView
-            :view="activeView"
-            :snapshot="store.snapshot"
-            :routing="store.routing"
-            @create-project="store.createProject"
-            @create-task="store.createTask"
-            @update-task-state="store.updateTaskState"
-          />
-        </template>
-      </section>
-    </main>
-    <ToastContainer />
-  </div>
+  <RouterView />
+  <ToastContainer />
 </template>
-
-<style scoped>
-.shell {
-  display: flex;
-  height: 100vh;
-  overflow: hidden;
-}
-
-main {
-  flex: 1;
-  display: flex;
-  flex-direction: column;
-  min-width: 0;
-  position: relative;
-  z-index: 1;
-}
-
-.content {
-  flex: 1;
-  overflow-y: auto;
-  padding: 20px;
-}
-
-.page-heading {
-  display: flex;
-  align-items: flex-start;
-  justify-content: space-between;
-  margin-bottom: 20px;
-  gap: 12px;
-}
-.page-heading h1 { margin: 0; font-size: 18px; }
-.page-heading p { margin: 4px 0 0; font-size: 10px; color: var(--nx-text-dim); }
-.eyebrow {
-  font-size: 8.5px;
-  font-weight: 700;
-  letter-spacing: .12em;
-  color: var(--nx-accent);
-  text-transform: uppercase;
-}
-.refresh {
-  display: flex;
-  align-items: center;
-  gap: 5px;
-  flex-shrink: 0;
-  padding: 6px 11px;
-  border: 1px solid var(--nx-line);
-  border-radius: 6px;
-  background: transparent;
-  color: var(--nx-text-dim);
-  font-size: 9px;
-  cursor: pointer;
-  transition: background .15s;
-}
-.refresh:hover { background: var(--nx-accent-soft); color: #d8dbe3; }
-
-.spin { animation: spin 1s linear infinite; }
-@keyframes spin { to { transform: rotate(360deg); } }
-
-@media (max-width: 860px) {
-  .kanban { grid-template-columns: 1fr; }
-}
-</style>