Add gzip compression and caching for static assets

The admin UI is a traditional multi-page app that loads ~13 separate
vendor/app JS+CSS files on every full navigation; none were compressed and
Cache-Control was max-age=0 (Express's default), forcing a revalidation
round-trip for every asset on every page view. Add gzip (compression
middleware) and sane Cache-Control (7d for vendor libs under
/static-modules, 1h for the app's own /static JS/CSS, which isn't
cache-busted). Matches the equivalent fix in theta42/proxy.

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

nodejs/package.json

@@ -26,6 +26,7 @@
     "@simpleworkjs/conf": "^1.1.0",
     "bcrypt": "^6.0.0",
     "bootstrap": "^5.3.8",
+    "compression": "^1.8.1",
     "ejs": "^3.1.10",
     "express": "^5.2.1",
     "express-rate-limit": "^8.5.2",