fix(overseerr,jellyseerr): fix Seerr migration corrupting /usr/bin/update (#12529)

The migration wrote the new update script directly to /usr/bin/update
while the parent shell still had the file open for reading. Since the
new content (with shebang) is longer than the original single-line file,
bash would read leftover bytes from the new content after the child
process exited, causing:
  /usr/bin/update: line 2: syntax error near unexpected token )'

Fix: write to a temp file first, then mv over /usr/bin/update. This
replaces the inode so the parent shell's fd sees EOF on the old
(unlinked) inode instead of reading into the new content.

ct/jellyseerr.sh

@@ -45,14 +45,16 @@ function update_script() {
     fi
 
     msg_info "Switching update script to Seerr"
-    cat <<'EOF' >/usr/bin/update
+    TMP_UPDATE=$(mktemp)
+    cat <<'EOF' >"$TMP_UPDATE"
 #!/usr/bin/env bash
 bash -c "$(curl -fsSL https://raw.githubusercontent.com/community-scripts/ProxmoxVE/main/ct/seerr.sh)"
 EOF
+    mv "$TMP_UPDATE" /usr/bin/update
     chmod +x /usr/bin/update
     msg_ok "Switched update script to Seerr"
     msg_warn "Please type 'update' again to complete the migration"
-    exit
+    exit 0
   fi
 
   msg_info "Updating Jellyseerr"

ct/overseerr.sh

@@ -44,10 +44,12 @@ function update_script() {
     fi
 
     msg_info "Switching update script to Seerr"
-    cat <<'EOF' >/usr/bin/update
+    TMP_UPDATE=$(mktemp)
+    cat <<'EOF' >"$TMP_UPDATE"
 #!/usr/bin/env bash
 bash -c "$(curl -fsSL https://raw.githubusercontent.com/community-scripts/ProxmoxVE/main/ct/seerr.sh)"
 EOF
+    mv "$TMP_UPDATE" /usr/bin/update
     chmod +x /usr/bin/update
     msg_ok "Switched update script to Seerr"
     msg_warn "Please type 'update' again to complete the migration"