docs/hub: update Element Calling port guidance to the new port set

User-facing polish to match the element-calling port changes:

- helpers.js: port-forward guide example now shows the 40000-40099 range
  instead of the removed 30000-40000.
- versions.json: livekit dev fallback 1.5.2 -> 1.13.6 (the Nix-generated
  version in sovran-hub.nix already derives from pkgs.livekit.version).
- server.py: docstring/comment examples reference 40000-40099.
- CHANGELOG.md: record the calling changes under [Unreleased].

The tile/modal port tables themselves are data-driven from server.py's
port_requirements / _PORTS_ELEMENT_CALLING (updated in the previous commit),
so no further UI changes are needed.

app/sovran_systemsos_web/versions.json

@@ -10,7 +10,7 @@
   "albyhub.service": "1.24.0",
   "mempool.service": "3.2.1",
   "matrix-synapse.service": "1.115.0",
-  "livekit.service": "1.5.2",
+  "livekit.service": "1.13.6",
   "vaultwarden.service": "1.32.0",
   "haven-relay.service": "0.1.0"
 }