test: bump version to 1.15.5 to test desktop build workflow

This simulates an automated version update to verify that:
- Desktop build workflow detects version changes in constants file
- Desktop assets are included in GitHub releases
- Unified versioning system works end-to-end

Author: rui-typelets

apps/desktop/package.json

@@ -1,6 +1,6 @@
 {
   "name": "typelets-desktop",
-  "version": "1.15.3",
+  "version": "1.15.5",
   "description": "Typelets Desktop - Secure Note Taking App",
   "main": "dist/main.js",
   "author": "Typelets Team",

src/constants/version.ts

@@ -1 +1 @@
-export const APP_VERSION = '1.15.4';
+export const APP_VERSION = '1.15.5';