feat: decommission server.sweet.home

Removes all flake artifacts for the retired NFS/ZFS file server:
- flake.nix: drop linode-server, proxmox-server, lxc-server targets
- hosts/server/: delete host identity
- modules/build-types/server.nix: delete build type (ZFS pool + NFS exports)
- vars/per-machine/{linode,lxc,proxmox}-server/: delete clan vars
- secrets/server.keytab: delete IPA keytab
- .sops.yaml: remove server key anchors, strip from common.yaml recipients,
  delete server.yaml and server.keytab creation rules
- variables.nix: remove serverIp, serverStorageIp (nfsServerHost/storageRoot
  retained — pxe-boot/mount-pxe-images.nix still references them)
- docs: mark server decommissioned in ip-addressing.md

Docker NFS mounts already pointed at nfs.storage.home (previous commit).
VM destruction and DNS cleanup (server.sweet.home, server.storage.home
A/PTR records) to follow once the VM is confirmed stopped.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J8djTWdXVzXZc99iujU6T2

.sops.yaml

@@ -7,20 +7,17 @@ keys:
   - &linode-gui age1hrx8qj02fj2ea6d4g9vqhyj9hl7fppkjqfdx2l37py3h6pdkr95s8n8rvs
   - &linode-minimal age1e7l8dusgmgfzd2cxrrzwepzjxt69hzqj4epee0cs27u6yg4kxcuqm34ncx
   - &linode-nix-cache age1jcx3yajjhghn8qh8za3yeu8nxykzlg3p4nrv03vnfvzl0mzayg2qmg940e
-  - &linode-server age1sweerhrga9yf8x6sv0apz4ed4g48rnlcq34rpv20t0rcelwgpgeqwvndzz
   - &linode-tailscale-router age1f7usptjx9rv4rxauasve200gxtdt9jkqhhdqstlf20wvlm7u75rsjfw50m
   - &lxc-docker age17jqc66x9yeshfgd9v78mj483r4zzarqdtuxtrkxe4x5mw679gphshd94th
   - &lxc-minimal age1px0h5l9zp2dww0m8fncrc82kfdmzplsfv2ltat7sna28xpg09pqqcl3s2k
   - &lxc-nix-cache age1ufg390ydrmma849t9xfkxxl5xvdkk6mngnlzhmy7mvuaje8sgcmsmnq6l7
   - &lxc-pxe-boot age16j42pdc5dr6wnj7xayhkqdj2rny9u68fcqejs50hqq42scssh4gsnrrnlt
-  - &lxc-server age1nruncs4l0ufk7yuc4des8p99c0alfndl0lhsws8tycl5pplfp56s30af5f
   - &lxc-tailscale-router age1k7d2du5mejsmv5rzavm4xwgpthqvcfsehduquv28nzs53zppa3kqngfxq2
   - &lxc-tor-relay age16kqfmvz4e23hmdlqresnyw69ej604s320mmd49h4hm3fhqchtgyqrws0k2
   - &proxmox-docker age1arhf2q45zw6wf2uevju4savp575x3m2tfvved5zzq3ay92ynua9s3cm92c
   - &proxmox-gui age19mn8zrxl8zpps9yvrh4euquvygpp4fp8queg7xc6qhtnl4ng8c9qx02qwn
   - &proxmox-nix-cache age1jlltcv5jcnm40z5k0q6hv053k2rqpqvemtuecdwn527uw8uqz4es3x7m68
   - &proxmox-pxe-boot age1ug787sgt6st6k82fgkrug2lzltw4qsukrrqqs3w27ewwqj8rg4hsxcmylz
-  - &proxmox-server age1529taqdwr6t0w7cvzmty0d5y5593wffl0krt48j6uc4u39k56g2qf6ywtp
   - &proxmox-tailscale-router age1zhfyuzlq40reuqlr34gf77852nhs3t6mqfzrqmas8z6sxk7tcfhsungrm0
   - &proxmox-ha-server-1 age1k73g8x47hs93wcv7qh92n3htz8pl295g49hyvlrf3570mts0hgys5g04d6
   - &proxmox-ha-server-2 age1fefy6dk8zn5c3edwmrs9vwx79quftnt784m628t9e34q3ft3cehqz8u72r
@@ -41,20 +38,17 @@ creation_rules:
           - *linode-gui
           - *linode-minimal
           - *linode-nix-cache
-          - *linode-server
           - *linode-tailscale-router
           - *lxc-docker
           - *lxc-minimal
           - *lxc-nix-cache
           - *lxc-pxe-boot
-          - *lxc-server
           - *lxc-tailscale-router
           - *lxc-tor-relay
           - *proxmox-docker
           - *proxmox-gui
           - *proxmox-nix-cache
           - *proxmox-pxe-boot
-          - *proxmox-server
           - *proxmox-tailscale-router
           - *proxmox-ha-server-1
           - *proxmox-ha-server-2
@@ -67,14 +61,6 @@ creation_rules:
           - *lxc-nix-cache
           - *proxmox-nix-cache
 
-  - path_regex: secrets/server\.yaml$
-    key_groups:
-      - age:
-          - *admin
-          - *linode-server
-          - *lxc-server
-          - *proxmox-server
-
   - path_regex: secrets/tor-relay\.yaml$
     key_groups:
       - age:
@@ -174,14 +160,6 @@ creation_rules:
           - *proxmox-gui
           - *linode-gui
 
-  - path_regex: secrets/server\.keytab$
-    key_groups:
-      - age:
-          - *admin
-          - *linode-server
-          - *lxc-server
-          - *proxmox-server
-
   - path_regex: secrets/docker\.keytab$
     key_groups:
       - age: