* FileBrowser Quantum: safer update (tmp download + atomic replace + arch autodetect)
**What**
Safer updater for FileBrowser Quantum addon:
- Download to temp file, then atomic `mv` into INSTALL_PATH
- Stop/start service around the swap
- CPU arch autodetect (amd64/arm64/armv7/armv6)
- Proper error handling & version verification before printing success
**Why**
Current update streams `curl` directly to `/usr/local/bin/filebrowser` and prints success even if `curl` fails.
I hit:
* fix(filebrowser-quantum): add missing `fi` before install section
Closes the conditional started with `if [[ -f "$INSTALL_PATH" ]]` so the script doesn’t hit a bash syntax error when reaching the install path.
* refactor(update): minimal fix - temp file + atomic mv; amd64 only
* style(update): remove comments/blank lines; drop restart (alpine-safe)
