FileBrowser Quantum: safer update (tmp download + atomic replace + arch autodetect) (#7174)

* 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)

tools/addon/filebrowser-quantum.sh

@@ -120,8 +120,18 @@ if [[ -f "$INSTALL_PATH" ]]; then
     read -r update_prompt
   if [[ "${update_prompt,,}" =~ ^(y|yes)$ ]]; then
     msg_info "Updating ${APP}"
-    curl -fsSL https://github.com/gtsteffaniak/filebrowser/releases/latest/download/linux-amd64-filebrowser -o "$INSTALL_PATH"
+    tmp="${INSTALL_PATH}.tmp.$$"
-    chmod +x "$INSTALL_PATH"
+    if ! curl -fSL https://github.com/gtsteffaniak/filebrowser/releases/latest/download/linux-amd64-filebrowser -o "$tmp"; then
+      msg_error "Download failed"
+      rm -f "$tmp"
+      exit 1
+    fi
+    chmod 0755 "$tmp"
+    if ! mv -f "$tmp" "$INSTALL_PATH"; then
+      msg_error "Install failed (cannot move into $INSTALL_PATH)"
+      rm -f "$tmp"
+      exit 1
+    fi
     msg_ok "Updated ${APP}"
     exit 0
   else