I have just fixed most of website after a couple of hours of outage.
The primary cause was my stupid and reckless decision to upgrade to debian jessie (was still running on squeeze and getting security warnings from my hosting company).
Debian upgrade should be simple process, right? At least in theory.
In practice sqeeze->wheeze->jessie broke grub settings, so reboot failed. Which is not fun when your system is 600km away... After fixing that, I have found that filesystem for some reason is corrupted to that... reboot failed. Fixed that and apache refused to start because of broken PHP...
For now, redmine is still broken - will still need to fix Ruby etc... It might stay broken for a while, a week or two.