feat(demo): start the demo in the round Fjord Night theme

A visitor without a chosen theme on this device sees the demo in
fjord-night instead of the square default; a chosen theme stays and
real installations are unchanged.

Release v0.27.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "mindsift-frontend",
-  "version": "0.26.1",
+  "version": "0.27.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "mindsift-frontend",
-      "version": "0.26.1",
+      "version": "0.27.0",
       "license": "Unlicense",
       "dependencies": {
         "@fontsource-variable/inter": "5.3.0",