Add log rotation settings

[obscurerichard]

This is at least a partial fix for:

• [Bug] logs are not rotating as expected, leading to disk space exhaustion #178

(I'm testing this today, will comment further on how it goes)

I see the support for backend/.env had been removed in compose.yml also recently - but this is really useful for setting non-default settings, so this adds it back.

[obscurerichard]

I set this to keep 240 logs and rotate every hour, and after a bit more than an hour the internal logs directory looks like:

root@2c5c3136b064:/app/backend# ls -l logs
total 1188
-rw-r--r--. 1 root root 478605 Mar 31 19:00 debug.json
-rw-r--r--. 1 root root 736792 Mar 31 18:49 debug.json.0
-rw-r--r--. 1 root root      0 Mar 31 19:00 error.json
-rw-r--r--. 1 root root      0 Mar 31 18:37 error.json.0

So I'd say this is working as expected.