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/lib/types.ts

@@ -74,6 +74,18 @@ export interface AircraftTrack {
   last_seen: string;
 }
 
+export interface VesselTrack {
+  mmsi: string;
+  org_id?: string;
+  node_id: string;
+  name: string | null;
+  lat: number | null;
+  lon: number | null;
+  speed_kt: number | null;
+  heading_deg: number | null;
+  last_seen: string;
+}
+
 export interface VocabularyPendingTerm {
   term: string;
   source: "induction" | "correction";