syncthing: Update to 1.29.2 and Change logfile path

syncthing: Update to 1.29.2 and Change logfile path

Update to 1.29.2 and Change logfile path from /etc/syncthing/syncthing
log to /var/log/syncthing.log.
This utilizes tmpfs (memory-based storage) to prevent disk usage growth
caused by log file accumulation during extended operation.

Benefits:
- Avoids storage saturation from excessive log growth.
- Aligns with best practices for temporary log management.
- For systems using flash storage (e.g., SSDs or eMMC), storing logs in
  tmpfs avoids flash memory wear caused by frequent writes to
  /etc/syncthing.

Signed-off-by: Yun Wang <maoerpet@foxmail.com>