fix: wire vars.nfsShares.options and correct stale share key names

- Filter non-attrset values from nfsShares in server.nix so the
  poolDatasets loop skips the new `options` string entry
- Fix typo proxomoxLxcImages → proxmoxLxcImages in server.nix exports
- Rename proxmoxPxeImages → pxebootImages in mount-pxe-images.nix and
  pxe-boot.nix to match the actual key in variables.nix

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/build-types/server.nix

@@ -10,7 +10,8 @@ let
     in lib.imap1 (i: _: lib.concatStringsSep "/" (lib.take i parts)) parts;
 
   poolDatasets = lib.unique (
-    lib.concatMap (share: ancestors share.subpath) (lib.attrValues vars.nfsShares)
+    lib.concatMap (share: ancestors share.subpath)
+      (lib.filter builtins.isAttrs (lib.attrValues vars.nfsShares))
   );
 in
 {
@@ -84,7 +85,7 @@ in
       ${vars.storageRoot}/${vars.nfsShares.nextcloudData.subpath} ${vars.lanCidr}${vars.nfsShares.options}
       ${vars.storageRoot}/${vars.nfsShares.raspiVolumes.subpath} ${vars.lanCidr}${vars.nfsShares.options}
       ${vars.storageRoot}/${vars.nfsShares.proxmoxIsos.subpath} ${vars.lanCidr}${vars.nfsShares.options}
-      ${vars.storageRoot}/${vars.nfsShares.proxomoxLxcImages.subpath} ${vars.lanCidr}${vars.nfsShares.options}
+      ${vars.storageRoot}/${vars.nfsShares.proxmoxLxcImages.subpath} ${vars.lanCidr}${vars.nfsShares.options}
       ${vars.storageRoot}/${vars.nfsShares.pxebootImages.subpath} ${vars.lanCidr}${vars.nfsShares.options}
     '';
   };