Header: replace My Account nav link with an account icon in the top right (sign-in link / account menu), collapse header below 900px; v2.23.0

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

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "siteforge",
-  "version": "2.22.1",
+  "version": "2.23.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "siteforge",
-      "version": "2.22.1",
+      "version": "2.23.0",
       "dependencies": {
         "@aws-sdk/client-s3": "^3.1135.0",
         "@dnd-kit/core": "^6.3.1",