feat(web/mazenet): amber-tint pending LAN placeholders

Pre: optimistic placeholders for enqueued LAN-add mutations were
indistinguishable from regular not-yet-deployed nets — same dim
mono chrome, same dotted border. User couldn't tell whether a drop
had been queued or had silently failed and re-stacked over an
existing LAN.

Tag the placeholder with `pending: true`, render it in the same
amber the REAP button uses (var(--warn, #e0a040)) with a 'PENDING'
chip-mini in the head. Visual is loud enough that there is no
chance of confusion with INACTIVE (dimmed) or regular pending-state
LANs (mono).

Reconciliation is the existing refetch pumping setNets(h.nets) on
SSE — no extra plumbing needed; placeholders disappear naturally
when the mutator's applied event lands and the canvas re-hydrates
from the server.

decnet_web/src/components/MazeNET/NetBox.tsx

@@ -27,6 +27,7 @@ const NetBox: React.FC<Props> = ({
     dropTarget ? 'drop-target' : '',
     inactive ? 'inactive' : '',
     deployed ? 'deployed' : '',
+    net.pending ? 'pending' : '',
   ].filter(Boolean).join(' ');
 
   const Icon = net.kind === 'internet' ? Globe : net.kind === 'dmz' ? ShieldAlert : GitMerge;
@@ -53,12 +54,20 @@ const NetBox: React.FC<Props> = ({
         <div style={{ display: 'flex', gap: 8, alignItems: 'center' }}>
           <Icon size={10} />
           <span>{net.label}</span>
-          {inactive && (
+          {inactive && !net.pending && (
             <span className="chip-mini"
                   style={{ marginLeft: 4, borderColor: 'var(--border)', color: 'rgba(255,255,255,0.45)' }}>
               INACTIVE
             </span>
           )}
+          {net.pending && (
+            <span className="chip-mini"
+                  style={{ marginLeft: 4,
+                           borderColor: 'var(--warn, #e0a040)',
+                           color: 'var(--warn, #e0a040)' }}>
+              PENDING
+            </span>
+          )}
         </div>
         <span className="cidr">{net.cidr}</span>
       </div>