refactor(viridian): migrate service data to dedicated BTRFS subvolumes

Migrate from path-based persistence (/persist/var/lib/*) to dedicated
BTRFS subvolumes for better data isolation and snapshot capabilities.

- Move valuable user-facing services to /srv/* with srv-* subvolumes:
  - forgejo: git repositories and database
  - opengist: paste data
  - minecraft: game world data
  - lighttpd: static web content
  - containers: OCI container volumes

- Update home directory to use hm-sajenim subvolume on viridian disk
- Remove jupyterhub service (no longer in use)
- Update borgbackup paths to match new service locations
- Follow upstream service defaults where possible for maintainability

Services kept on /persist (disposable state):
- traefik, crowdsec, murmur

nixos/viridian/services/minecraft/default.nix

@@ -5,6 +5,7 @@
   config,
   ...
 }: let
+  hostname = config.networking.hostName;
   modpack = pkgs.fetchPackwizModpack rec {
     version = "9083262";
     url = "https://raw.githubusercontent.com/sajenim/minecraft-modpack/${version}/pack.toml";
@@ -71,9 +72,6 @@ in {
       };
     };
 
-    # Each server will be under a subdirectory named after the server name.
-    dataDir = "/var/lib/minecraft";
-
     # Open firewall for all servers.
     openFirewall = true;
     
@@ -106,14 +104,12 @@ in {
     };
   };
 
-  # Enable persistence for the data directory.
-  environment.persistence."/persist" = {
-    directories = [
-      {
-        directory = "/var/lib/minecraft";
-        user = "minecraft";
-        group = "minecraft";
-      }
+  fileSystems."/srv/minecraft" = {
+    device = "/dev/disk/by-label/${hostname}";
+    fsType = "btrfs";
+    options = [
+      "subvol=srv-minecraft"
+      "compress=zstd"
     ];
   };
 }