Fix cleanup issues in npm cache and rustup toolchain (#10107)

Issue 1 - BentoPDF (npm cache clean failure):
- npm cache clean --force can fail with ENOTEMPTY on corrupted caches
- Added npm cache verify before clean to detect/fix corruption
- Explicitly redirect stderr to suppress error noise

Issue 2 - Linkwarden (rustup toolchain removed too early):
- Script deleted ~/.rustup during build cleanup
- Later cleanup_lxc() tried to run 'cargo clean' without toolchain
- Now only remove cargo cache dirs, preserve ~/.rustup toolchain

Files changed:
- misc/core.func (cleanup_lxc function)
- install/linkwarden-install.sh (install script)
- ct/linkwarden.sh (update function)

Both changes improve reliability of container cleanup process.

ct/linkwarden.sh

@@ -52,7 +52,7 @@ function update_script() {
     $STD yarn web:build
     $STD yarn prisma:deploy
     [ -d /opt/data.bak ] && mv /opt/data.bak /opt/linkwarden/data
-    rm -rf ~/.cargo/registry ~/.cargo/git ~/.cargo/.package-cache ~/.rustup
+    rm -rf ~/.cargo/registry ~/.cargo/git ~/.cargo/.package-cache
     rm -rf /root/.cache/yarn
     rm -rf /opt/linkwarden/.next/cache
     msg_ok "Updated ${APP}"