Air-gap fixes + in-app /docs (README/DEPLOYMENT/api.md/docs/*)

Air-gap:
- DynamicRecord.refreshAll() called getPublicIp() (api.ipify.org,
  icanhazip.com, ifconfig.me) every 4h on a timer regardless of
  whether any dynamic records were configured -- the one background
  call in the repo not actually gated by feature use. Now skips the
  lookup entirely when there's nothing to refresh.
- Removed the stray, unauthenticated GET /test page (a leftover
  jq-repeat demo) that loaded jQuery + Mustache from external CDNs.
- Removed a dead IE<9-only html5shim script tag pointing at a domain
  that no longer resolves.

Docs:
- New GET /docs (index) and /docs/:slug routes render this project's
  own README, DEPLOYMENT, api.md, and docs/*.md server-side via
  marked (new dependency) -- so the documentation is readable from
  the running app with no route to GitHub Pages, where it otherwise
  only lives. Public, no auth, same tier as the health endpoint.
- .dockerignore/Dockerfile updated: docs/, DEPLOYMENT.md, and
  nodejs/api.md were previously excluded from the image entirely
  ("served via GitHub Pages, not from the image") -- now copied in
  alongside README.md/tos.md-style, since they're needed at runtime.

nodejs/package-lock.json

@@ -25,6 +25,7 @@
         "jquery": "^4.0.0",
         "ldapts": "^8.1.8",
         "linux-sys-user": "^1.2.0",
+        "marked": "^9.1.6",
         "model-redis": "^1.5.0",
         "moment": "^2.30.1",
         "mustache": "^4.2.0",
@@ -1410,6 +1411,18 @@
       "integrity": "sha512-TyPFnk3kp9kplKPjWtYYbezYzj+Xe47bGu3YZs2Jg3xxLUw/ny0AHL252jpR1c8q32vIQxWK8qLpFZ+qHHC0MQ==",
       "license": "MIT"
     },
+    "node_modules/marked": {
+      "version": "9.1.6",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-9.1.6.tgz",
+      "integrity": "sha512-jcByLnIFkd5gSXZmjNvS1TlmRhCXZjIzHYlaGkPlLIekG55JDR2Z4va9tZwCiP+/RDERiNhMOFu01xd6O5ct1Q==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 16"
+      }
+    },
     "node_modules/math-intrinsics": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/math-intrinsics/-/math-intrinsics-1.1.0.tgz",