cinny: allow matrix.org logins on the Lotus client

Add matrix.org to homeserverList so federated friends with matrix.org accounts
can sign into chat.lotusguild.org. defaultHomeserver stays 0 (lotusguild), and
allowCustomHomeservers stays false — only the two listed servers are selectable,
so the client isn't opened up to arbitrary homeservers.

Deploys via lxc106-cinny.sh (cp -> /var/www/html/config.json); lotus-build.sh
preserves the live config across app rebuilds, so this is the authoritative copy.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cinny/config.json

@@ -1,7 +1,8 @@
 {
   "defaultHomeserver": 0,
   "homeserverList": [
-    "matrix.lotusguild.org"
+    "matrix.lotusguild.org",
+    "matrix.org"
   ],
   "allowCustomHomeservers": false,
   "featuredCommunities": {