perf: frontend request cache, poll pause, and code-split shell (#1052)

Host/status caching, shell code-split, SSH pool waits, host-metrics concurrency, background-tab idle, per-host status subscriptions, homepage poll quieting, and virtualized host sidebar + file manager lists.

package-lock.json

@@ -11,6 +11,7 @@
       "dependencies": {
         "@simplewebauthn/browser": "^13.3.0",
         "@simplewebauthn/server": "^13.3.2",
+        "@tanstack/react-virtual": "^3.14.6",
         "@types/ldapjs": "^3.0.6",
         "axios": "^1.18.1",
         "bcryptjs": "^3.0.3",
@@ -6694,6 +6695,33 @@
         "vite": "^5.2.0 || ^6 || ^7 || ^8"
       }
     },
+    "node_modules/@tanstack/react-virtual": {
+      "version": "3.14.6",
+      "resolved": "https://registry.npmjs.org/@tanstack/react-virtual/-/react-virtual-3.14.6.tgz",
+      "integrity": "sha512-4+Uq8m0/gzO4kMCHUEpTtGX1RnONK0C+g88b2ltwPMWUBiaVarBuWKoPJaz7gj1cKCVRAdyu+U8GcKhwCc2beA==",
+      "license": "MIT",
+      "dependencies": {
+        "@tanstack/virtual-core": "3.17.4"
+      },
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      },
+      "peerDependencies": {
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0",
+        "react-dom": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
+    "node_modules/@tanstack/virtual-core": {
+      "version": "3.17.4",
+      "resolved": "https://registry.npmjs.org/@tanstack/virtual-core/-/virtual-core-3.17.4.tgz",
+      "integrity": "sha512-nGm5KteqxasUdThLc2izl6dHUqLv0LQj7Nuyo5gYalTPf/U8a9ermvsl7reT+6ioBW1l8WfpP/mcU338nLXpqw==",
+      "license": "MIT",
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      }
+    },
     "node_modules/@testing-library/dom": {
       "version": "10.4.1",
       "resolved": "https://registry.npmjs.org/@testing-library/dom/-/dom-10.4.1.tgz",