nixos/immich: fix .host option not working

[Zocker1999NET]

Things done

This PR fixes the services.immich.host option, which does not work with the current version of Immich in unstable (1.117.0). I verified that the current version does not work by using following configuration & checking the journal of the immich service:

services.immich = {
  enable = true;
  host = "0.0.0.0"; # IPv6 as well
  openFirewall = true;
  port = 3001;
};

Oct 10 23:00:33 immich server[993]: [Nest] 993  - 10/10/2024, 11:00:33 PM     LOG [Api:Bootstrap] Immich Server is listening on http://127.0.0.1:3001 [v1.117.0] [PRODUCTION] 

The Immich doc says the correct environment variable is called IMMICH_HOST, see https://immich.app/docs/install/environment-variables/#ports.
I tested that this works in my configuration, which looks like this (extract):

services.immich = {
  enable = true;
  # TODO (until PR) host option not working
  environment.IMMICH_HOST = "0.0.0.0"; # IPv6 as well
  openFirewall = true;
  port = 3001;
};

Oct 10 23:03:45 immich server[1606]: [Nest] 1606  - 10/10/2024, 11:03:45 PM     LOG [Api:Bootstrap] Immich Server is listening on http://[::1]:3001 [v1.117.0] [PRODUCTION] 

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[Zocker1999NET]

ups, sorry for the premature PR. I assumed that my fix was working as I misread http://[::1]:3001 in the latest log for http://[::]:3001 & together with what I found in the Immich docs, I now assumed that my router VM was creating the connectivity issues. Now after finding my mistake & digging further in the Immich code, the current module implementation could be already working, assuming this is the affecting code:
https://github.com/immich-app/immich/blob/8daa8073ae3a8e69ba410d0184006915995bf6ad/server/src/workers/api.ts#L18

But nontheless I do not get Immich to listen to all interfaces instead of localhost (I want to avoid to hardcode the VM’s IP there). When I find success, I will update the docs of the module accordingly (but in a new PR).