Wire AIS end to end: telemetry ingestion + live map overlay

node-26#9, same shape as the ADS-B commit. Adds POST /telemetry/ais
(same node-key auth, same org_id-stamped upsert-by-key pattern, this time
by mmsi into a new `vessels` collection) and its docInMyOrg() firestore
rule. Frontend gets useVessels() (mirrors useAircraft(), longer staleness
window since AIS position reports are minutes apart, not seconds) and an
opt-in "Vessels" map overlay.

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

drb-frontend/components/MapView.tsx

@@ -16,6 +16,7 @@ import type { CallRecord, IncidentRecord, NodeRecord, NodeStatus } from "@/lib/t
 import { isKnownSeverity, SEVERITY_COLORS, SEVERITY_LABEL, type Severity } from "@/lib/severity";
 import { MachineOutputNotice } from "@/components/ui/MachineOutputNotice";
 import { useAircraft } from "@/lib/useAircraft";
+import { useVessels } from "@/lib/useVessels";
 
 // ── Leaflet icon fix ──────────────────────────────────────────────────────────
 delete (L.Icon.Default.prototype as unknown as Record<string, unknown>)._getIconUrl;
@@ -125,6 +126,39 @@ function AircraftLayer() {
   );
 }
 
+// ── Vessel icon — node-26#9 second-SDR AIS overlay ─────────────────────────────
+function vesselIcon(headingDeg: number | null): L.DivIcon {
+  const size = 14;
+  const rotation = headingDeg ?? 0;
+  return L.divIcon({
+    className: "",
+    html: `<div style="width:${size}px;height:${size}px;transform:rotate(${rotation}deg)"><svg width="${size}" height="${size}" viewBox="0 0 24 24" fill="var(--accent)" stroke="var(--surface)" stroke-width="1"><path d="M12 2 L18 14 L18 20 L6 20 L6 14 Z"/></svg></div>`,
+    iconSize: [size, size],
+    iconAnchor: [size / 2, size / 2],
+  });
+}
+
+function VesselLayer() {
+  const { vessels } = useVessels();
+  return (
+    <>
+      {vessels
+        .filter((v) => v.lat != null && v.lon != null)
+        .map((v) => (
+          <Marker key={v.mmsi} position={[v.lat as number, v.lon as number]} icon={vesselIcon(v.heading_deg)}>
+            <Popup minWidth={160}>
+              <div className="space-y-1">
+                <div className="font-semibold">{v.name || v.mmsi}</div>
+                <div className="text-xs text-ink-muted">MMSI {v.mmsi}</div>
+                {v.speed_kt != null && <div className="text-xs">Speed: {Math.round(v.speed_kt)} kt</div>}
+              </div>
+            </Popup>
+          </Marker>
+        ))}
+    </>
+  );
+}
+
 function nodeFanIcon(members: NodeRecord[]): L.DivIcon {
   const n = members.length;
   const CARD = 13;
@@ -619,6 +653,13 @@ export default function MapView({ nodes, activeCalls, incidents = [], calls = []
             </FeatureGroup>
           </LayersControl.Overlay>
 
+          {/* Overlay: Vessels — node-26#9 second-SDR AIS live snapshot, opt-in */}
+          <LayersControl.Overlay name="Vessels">
+            <FeatureGroup>
+              <VesselLayer />
+            </FeatureGroup>
+          </LayersControl.Overlay>
+
           {/* Overlay: Weather Radar — NEXRAD via Iowa Env Mesonet; key forces remount on refresh */}
           <LayersControl.Overlay name="Weather Radar">
             <TileLayer