chore: update package.json versions to 1.6.0 (#75)

The release script created tag v1.6.0 but did not update the version
numbers in package.json files. This fix ensures the About modal
displays the correct version.

backend/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "medassist-ng-backend",
-  "version": "1.5.0",
+  "version": "1.6.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "medassist-ng-backend",
-      "version": "1.5.0",
+      "version": "1.6.0",
       "dependencies": {
         "@fastify/cookie": "^10.0.1",
         "@fastify/cors": "^10.0.1",

backend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "medassist-ng-backend",
-  "version": "1.5.0",
+  "version": "1.6.0",
   "private": true,
   "type": "module",
   "scripts": {