fix: remove desktop shortcut from NSIS installer by default

Tauri's NSIS bundler creates a desktop shortcut unconditionally. Added
a POSTINSTALL hook that deletes it immediately after creation. Start
menu shortcut remains. Users who want a desktop shortcut can create
one manually.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/tauri.conf.json

@@ -39,7 +39,8 @@
       "nsis": {
         "displayLanguageSelector": false,
         "installerIcon": "icons/icon.ico",
-        "installMode": "perMachine"
+        "installMode": "perMachine",
+        "installerHooks": "./windows/hooks.nsh"
       }
     }
   },

src-tauri/windows/hooks.nsh

@@ -0,0 +1,6 @@
+; Wraith NSIS installer hooks
+; Desktop shortcut is OFF by default — Tauri creates one, we remove it.
+
+!macro NSIS_HOOK_POSTINSTALL
+  Delete "$DESKTOP\${MAINBINARYNAME}.lnk"
+!macroend