Use a file for defining env vars in the service file

There currently isn't a nice way to define env vars outside of overriding the service, I suggest moving the current config from:

Environment="HOME=/var/lib/ollama" "GIN_MODE=release"

to:

EnvironmentFile=/etc/ollama.conf

Current workaround would be

# /etc/systemd/system/ollama.service.d/override.conf
[Service]
EnvironmentFile=/etc/ollama.conf
Environment=  

Use case:

I needed to bind it to something else and did all of this if anyone care:

# /etc/ollama.conf

# The host:port to bind to (default "127.0.0.1:11434")
OLLAMA_HOST=0.0.0.0:11434           

# A comma separated list of allowed origins.
OLLAMA_ORIGINS=*://localhost,*://192.168.1.40,*://192.168.1.10

# The path to the models directory (default is "~/.ollama/models")
OLLAMA_MODELS=/models/ollama

HOME=/var/lib/ollama
GIN_MODE=release

I've opened an issue upstream about providing a unit file, theirs is currently having the same Environment setup minus the hardening, but it's not even in the repo: https://github.com/ollama/ollama/issues/3516