Fix concurrency, security, and correctness issues across backend and frontend

- C1: Add sync.RWMutex to vm.Manager to protect concurrent vms map access
- H1: Fix IP arithmetic overflow in network slot addressing (byte truncation)
- H5: Fix MultiplexedChannel.Fork() TOCTOU race (move exited check inside lock)
- H8: Remove snapshot overwrite — return template_name_taken conflict instead
- H9: Wrap DeleteAccount DB ops in a transaction, make team deletion fatal
- H10: Sanitize serviceErrToHTTP to stop leaking internal error messages
- H11: Add deleted_at IS NULL to GetUserByEmail/GetUserByID queries
- H12: Add id DESC to audit log composite index for cursor pagination
- H15: Delete dead AuthModal.svelte component
- H17: Move JWT from WebSocket URL query param to first WS message
- H18: Fix $derived to $derived.by in FilesTab breadcrumbs

frontend/src/routes/admin/hosts/+page.svelte

@@ -294,6 +294,16 @@
 		</div>
 	</main>
 
+	<footer class="flex h-7 shrink-0 items-center justify-end border-t border-[var(--color-border)] bg-[var(--color-bg-1)] px-7">
+		<div class="flex items-center gap-1.5">
+			<span class="relative flex h-[5px] w-[5px]">
+				<span class="animate-status-ping absolute inline-flex h-full w-full rounded-full bg-[var(--color-accent)]"></span>
+				<span class="relative inline-flex h-[5px] w-[5px] rounded-full bg-[var(--color-accent)]"></span>
+			</span>
+			<span class="font-mono text-label uppercase tracking-[0.04em] text-[var(--color-text-secondary)]">All systems operational</span>
+		</div>
+	</footer>
+
 {#snippet skeletonRows()}
 	<div class="rounded-[var(--radius-card)] border border-[var(--color-border)] bg-[var(--color-bg-1)] overflow-hidden shadow-sm">
 		<table class="w-full">