Add errors for install dir edge cases (#6733)

## Summary
- show explicit validation errors when the install path lives inside the
desktop app bundle or updater cache
- include the new locale strings for these error prompts so the UI
surfaces actionable guidance

## Testing
- pnpm typecheck
- pnpm lint:fix

## Notes
Desktop types still need to be updated to include the new validation
flags; see https://github.com/Comfy-Org/desktop/pull/1400

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6733-Add-errors-for-install-dir-edge-cases-2af6d73d3650811bada6fc7dd72ecf68)
by [Unito](https://www.unito.io)

apps/desktop-ui/package.json

@@ -91,7 +91,7 @@
     "build-storybook": "storybook build -o dist/storybook"
   },
   "dependencies": {
-    "@comfyorg/comfyui-electron-types": "0.4.73-0",
+    "@comfyorg/comfyui-electron-types": "catalog:",
     "@comfyorg/shared-frontend-utils": "workspace:*",
     "@primevue/core": "catalog:",
     "@primevue/themes": "catalog:",