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.

misc/core.func

@@ -816,7 +816,10 @@ cleanup_lxc() {
   fi
 
   # Node.js npm
-  if command -v npm &>/dev/null; then $STD npm cache clean --force || true; fi
+  if command -v npm &>/dev/null; then
+    $STD npm cache verify 2>/dev/null || true
+    $STD npm cache clean --force 2>/dev/null || true
+  fi
   # Node.js yarn
   if command -v yarn &>/dev/null; then $STD yarn cache clean || true; fi
   # Node.js pnpm