Let admins hide the Proxmox-link card per server

Not every registered server is a Proxmox VM/LXC -- bare-metal boxes
and other hosts had no reason to show a "link to Proxmox" option, but
it appeared unconditionally on every server's detail page.

New hideProxmoxLink column on servers (default false, so existing
behavior is unchanged until someone opts in). A "Not a VM? Hide this"
link in the card's header sets it; once hidden, a small "+ Show
Proxmox link options" link takes its place so it's still reachable,
not buried in a settings form. The card always shows regardless of
this flag once a server IS actually linked, so unlinking never becomes
unreachable by hiding the card out from under an active link.

Verified against a temp SQLite DB with real migrations: a new server
defaults to false, and toggling true/false both persist correctly.

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

server/src/routes/servers.ts

@@ -96,6 +96,7 @@ const updateServerSchema = z
     proxmoxNode: z.string().nullable().optional(),
     proxmoxGuestType: z.enum(["qemu", "lxc"]).nullable().optional(),
     proxmoxVmid: z.number().int().nullable().optional(),
+    hideProxmoxLink: z.boolean().optional(),
   })
   .refine(
     (data) => {