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/borgbackup/default.nix

@@ -6,14 +6,13 @@
   services.borgbackup.jobs."borgbase" = {
     paths = [
       # Websites
-      "/srv/www/sajenim.dev"
+      "/srv/lighttpd/sajenim.dev"
       # Services
       "/var/lib/crowdsec"
       "/var/lib/forgejo"
-      "/var/lib/jupyterhub"
-      "/var/lib/minecraft"
       "/var/lib/opengist"
       "/var/lib/traefik"
+      "/srv/minecraft"
       # Multimedia
       "/srv/multimedia/containers/jellyfin"
       "/srv/multimedia/containers/lidarr"