Add Proxmox integration

Fifth live integration: VM/LXC status across every online node in the
cluster, with start/stop/restart actions — matching the "dashboard + basic
actions" depth from the plan. Adapter built against Proxmox VE's own
published API tree (pve.proxmox.com/pve-docs/api-viewer/apidoc.js — parsed
its ~4MB ExtJS tree structure directly since it's not plain JSON) plus
community-verified docs for the token auth header format, since the user's
instance isn't reachable from here.

server/src/integrations/proxmox/adapter.ts: GET /nodes for online nodes,
then GET /nodes/{node}/{qemu,lxc} per node in parallel (Promise.all) and
flattened, tagging each guest with its node and type; POST
/nodes/{node}/{qemu,lxc}/{vmid}/status/{start,stop,reboot} for actions (all
confirmed token-auth-eligible via the spec's "allowtoken" flag). Uses
node:https directly (like the cPanel DNS adapter) rather than fetch, since
Proxmox commonly runs a self-signed certificate in homelab setups — added
an "Allow self-signed certificate" checkbox field for that. Auth is
`Authorization: PVEAPIToken=<tokenId>=<tokenSecret>`, a different shape
from the other three integrations' single bearer token, so the field
schema splits it into two fields (a non-secret token ID like
"root@pam!homelab-manager" and a secret token value).

Verified: full build passes. Unreachable from here, so ran a 16-check HTTP
test against the live server: role gating, credential non-leakage,
disabled-integration blocking, invalid-guest-type and non-numeric-vmid
rejection, checkbox-only config correctly still failing required-field
validation, and the wrong_type crash-safety check for this fifth adapter
type — server stays up throughout. Real node/VM data and the actual
start/stop/restart actions still need verification once this app can reach
the user's Proxmox cluster.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

server/src/integrations/fieldSchemas.ts

@@ -27,6 +27,12 @@ export const INTEGRATION_FIELDS: Partial<Record<IntegrationType, IntegrationFiel
     { key: "url", label: "Semaphore URL", secret: false, placeholder: "https://semaphore.example.lan" },
     { key: "token", label: "API token", secret: true, type: "password" },
   ],
+  proxmox: [
+    { key: "url", label: "Proxmox URL", secret: false, placeholder: "https://pve.example.lan:8006" },
+    { key: "tokenId", label: "API token ID", secret: false, placeholder: "root@pam!homelab-manager" },
+    { key: "tokenSecret", label: "API token secret", secret: true, type: "password" },
+    { key: "insecure", label: "Allow self-signed certificate", secret: false, type: "checkbox" },
+  ],
 };
 
 /** Fixed base URL per integration type, stored on the row for display/reference. */