Rework log/sdt.log so that it works with .gitignore

[pleia2]

We currently ship with an empty sdt.log file, but once this file gets populated in production, it makes updates complicated because now there's a git diff. If we simply add it to .gitignore, we can't ship with that file.

Someone needs to look into whether the application will work without log/sdt.log existing as an empty file. If not, we'll need a slight modification to src/config/config.py to create that file if it doesn't exist, in addition to adding it to .gitignore.