refactor: move host configs under hosts/{jupiter,vps}

- git-mv jupiter/ vps/ into hosts/; fix ../ -> ../../ for common/services/secrets
- flake.nix + deploy point at hosts/<config>/
- README structure updated
- verified: jupiter/vps/vbox all eval

scripts/deploy

@@ -66,7 +66,7 @@ case "$cmd" in
     { [ -n "$config" ] && [ -n "$host" ]; } || die "usage: ./deploy install <config> <host>"
     hostkey="$HOME/.config/homelab/$config/ssh_host_ed25519_key"
     [ -f "$hostkey" ] || die "missing host key: $hostkey"
-    [ -d "./$config" ] || die "no ./$config directory in the repo"
+    [ -d "./hosts/$config" ] || die "no ./hosts/$config directory in the repo"
 
     # Stage the pre-generated SSH host key so sops can decrypt on boot #1.
     stage="$(mktemp -d)"
@@ -78,7 +78,7 @@ case "$cmd" in
     nix run github:nix-community/nixos-anywhere -- \
       --flake ".#$config" \
       --extra-files "$stage" \
-      --generate-hardware-config nixos-generate-config "./$config/hardware-configuration.nix" \
+      --generate-hardware-config nixos-generate-config "./hosts/$config/hardware-configuration.nix" \
       --target-host "root@$host"
     ;;