fix(transmission-done): rotate_log calls stat before checking file exists

[smartwatermelon]

Problem

In transmission-done.sh, rotate_log() (line ~1254) calls stat -f%z "${LOG_FILE}" unconditionally before checking if the file exists. On first run, this produces a stderr error message.

Source

Flagged by sentry[bot] on PR #108 (LOW severity). Pre-existing behavior imported from transmission-filebot.

Suggested fix

Move the stat call inside the if [[ -f "${LOG_FILE}" ]] block.