Replace nextcloud with nextcloud-vfs for virtual files support

- Change from nextcloud to nextcloud-vfs cask to enable virtual file support
- Users will need to manually uninstall old nextcloud before installing

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

install.sh

@@ -134,7 +134,7 @@ CASKS=(
   "deepl"            # DeepL translator
   "element"          # Matrix client
   "signal"           # Signal messenger
-  "nextcloud"        # Nextcloud sync
+  "nextcloud-vfs"    # Nextcloud sync (with virtual files support)
   "proton-drive"     # Proton Drive
   "proton-mail"      # Proton Mail
   "protonvpn"        # Proton VPN