Adopt @simpleworkjs/frontend's messages/modal/validate modules

Same swap as sso-manager-node/jump-host: vendored app.util.actionMessage/
actionConfirm replaced by @simpleworkjs/frontend's app.messages.action/
confirm (real HTML-escaping, toast fallback); vendored val.js replaced by
the package's app.validate.js.

proxy's host/target/hostname validation rules (mirrored from the backend's
utils/hostname_validate.js — wildcard DNS patterns, not something other
apps need) move to public/js/app.js, registered via $.validateSettings,
since they're proxy-specific and don't belong in the shared package's
generic rule set (eq/user/password/ip).

app.api/app.auth/app.pubsub/app.socket in app-base.js are untouched, same
reasoning as sso-manager-node's PR.

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

nodejs/package-lock.json

@@ -13,6 +13,7 @@
         "@popperjs/core": "^2.11.8",
         "@simpleworkjs/app-stack": "^1.0.0",
         "@simpleworkjs/conf": "^1.2.0",
+        "@simpleworkjs/frontend": "^0.2.5",
         "@simpleworkjs/ldap": "^1.0.0",
         "@simpleworkjs/oidc-client": "^1.0.0",
         "acme-client": "^5.4.0",
@@ -308,6 +309,15 @@
         "node": ">=16.0.0"
       }
     },
+    "node_modules/@simpleworkjs/frontend": {
+      "version": "0.2.5",
+      "resolved": "https://registry.npmjs.org/@simpleworkjs/frontend/-/frontend-0.2.5.tgz",
+      "integrity": "sha512-PxR7UVPv3gRpdF0WsuAZplF1vYvKsEJQevVPhz9d72U+69vP/OH3tlaAXjtO/apMHfhT1viOPw2gMVOrPSxYZw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=18.0.0"
+      }
+    },
     "node_modules/@simpleworkjs/ldap": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/@simpleworkjs/ldap/-/ldap-1.0.0.tgz",