feat(desktop): show the installed app's own version in the UI

Nothing displayed which desktop build was actually installed — debugging
a stuck update meant inferring the current version backwards from the
update prompt's target version. Added DesktopVersionBadge (next to the
existing server-side VersionBadge) using @tauri-apps/api's getVersion(),
the real running app version baked in from tauri.conf.json. No-ops in a
browser. Exported inTauri() from origin.ts instead of redefining it again.

apps/web/package.json

@@ -18,6 +18,7 @@
     "@radix-ui/react-tabs": "^1.1.15",
     "@tanstack/react-query": "^5.101.0",
     "@tanstack/react-router": "^1.170.16",
+    "@tauri-apps/api": "^2.11.1",
     "@tauri-apps/plugin-http": "^2.5.2",
     "@tauri-apps/plugin-process": "^2.3.1",
     "@tauri-apps/plugin-updater": "^2.10.1",