docs, hub, installer: say Server + Desktop makes the home IP public

Server + Desktop publishes services under the operator's own domain, and
the DNS record for that domain points at the home connection, so anyone
can look up the home IP address. None of the places that offer Server +
Desktop said so.

- README: new section "Server + Desktop and your home IP address" (what
  becomes public, what does not, the alternatives, and what happens
  technically), plus a note on the role table and in the security
  overview.
- SECURITY.md: a matching section, the consequence noted next to "Public
  web services exposed only when enabled by the operator", and the
  supported versions row no longer pins 1.0.x.
- ISO installer: the Server + Desktop role card ends with the warning.
- Hub: the domain setup text (onboarding, feature setup and domain
  reconfiguration share renderDomainNeedsHtml) and the upgrade dialog
  carry the same notice.
- Add tests/test_exposure_guards.py. It fails if one of these places
  loses the notice or the README anchor stops resolving.

tests/test_exposure_guards.py

@@ -0,0 +1,68 @@
+"""Guards for the home-IP warnings.
+
+Server + Desktop publishes the home IP address (the domain points at it), so every
+place that offers Server + Desktop must say so, and the README section they point
+at must exist.
+
+These read the shipped source files like the nix-file checks in test_security.py:
+nothing is run and nothing touches the network.
+"""
+
+import os
+import re
+import unittest
+
+_ROOT = os.path.normpath(os.path.join(os.path.dirname(__file__), ".."))
+_PHRASE = "home ip address"
+
+
+def _read(*parts):
+    with open(os.path.join(_ROOT, *parts), encoding="utf-8") as f:
+        return f.read()
+
+
+def _github_slug(heading):
+    slug = re.sub(r"[^\w\- ]", "", heading.strip().lower())
+    return slug.replace(" ", "-")
+
+
+class HomeIpWarnings(unittest.TestCase):
+
+    def test_installer_role_card(self):
+        src = _read("iso", "installer.py")
+        card = re.search(r'\("Server \+ Desktop",\s*"((?:[^"\\]|\\.)*)"', src, re.S)
+        self.assertIsNotNone(card, "Server + Desktop role card not found")
+        self.assertIn(_PHRASE, card.group(1).lower())
+
+    def test_hub_domain_setup_text(self):
+        # domain-prereqs.js is the single source for onboarding, feature setup
+        # and domain reconfiguration; the notice must follow every variant.
+        js = _read("app", "sovran_systemsos_web", "static", "js", "domain-prereqs.js")
+        body = js[js.index("function renderDomainNeedsHtml"):]
+        body = body[:body.index("\n}\n")]
+        self.assertIn(_PHRASE, body.lower())
+        self.assertGreater(body.lower().index(_PHRASE), body.rindex("} else {"),
+                           "the notice must come after the last variant, not inside one")
+
+    def test_hub_upgrade_dialog(self):
+        html = _read("app", "sovran_systemsos_web", "templates", "index.html")
+        dialog = html[html.index('id="upgrade-modal"'):html.index("Security Reset overlay")]
+        self.assertIn(_PHRASE, " ".join(dialog.lower().split()))
+
+    def test_readme_and_security_policy(self):
+        self.assertIn(_PHRASE, _read("README.md").lower())
+        self.assertIn(_PHRASE, " ".join(_read("SECURITY.md").lower().split()))
+
+    def test_links_to_the_readme_section_resolve(self):
+        readme = _read("README.md")
+        slugs = {_github_slug(m.group(2))
+                 for m in re.finditer(r"^(#{1,6})\s+(.+?)\s*$", readme, re.M)}
+        links = re.findall(r"\]\(#(server--desktop[^)]*)\)", readme)
+        links += re.findall(r"README\.md#(server--desktop[^)\s]*)", _read("SECURITY.md"))
+        self.assertTrue(links, "expected links to the home-IP section")
+        for anchor in links:
+            self.assertIn(anchor, slugs)
+
+
+if __name__ == "__main__":
+    unittest.main()