Add ADS-B, AIS, and ALPR map layers with live CoT streaming (#36)

## Summary

- **ADS-B & AIS:** OpenSky and AISStream OSINT feeds upsert into the CoT store; tactical tracks still arrive via adsbcot/aiscot on `:8089`. Map clients subscribe via `GET /api/cot/stream` (SSE) with viewport bbox filtering and Air / Surface / Team layer toggles.
- **ALPR (Flock/OSM):** Toggleable license-plate reader layer sourced from OpenStreetMap, with SQLite cache, Overpass fallback, tiled viewport fetching, and clustered markers with direction cones.
- **Map performance:** Ring-based tile selection (fixes zoom-out crash), immutable tile cache, incremental marker sync, split cluster load/query, and padded SSE bbox to reduce reconnect churn.

## Docs

- `docs/tracking.md` — ADS-B/AIS accuracy tiers, freshness, self-hosted receivers, optional OSINT API keys
- `docs/map-and-cameras.md` — ALPR layer and map behavior updates

---------

Co-authored-by: Madison Grubb <madison@elastiflow.com>
Reviewed-on: #36

server/plugins/cot.js

@@ -108,7 +108,7 @@ async function processFrame(socket, rawMessage, payload, authenticated) {
       socket.destroy()
       return
     }
-    updateFromCot(parsed).catch((err) => {
+    updateFromCot({ ...parsed, type: parsed.eventType }).catch((err) => {
       console.error('[cot] Error updating from CoT:', err?.message)
     })
     if (authenticated) broadcast(socket, rawMessage)

server/plugins/cotLifecycle.js

@@ -0,0 +1,32 @@
+import { registerCleanup } from '../utils/shutdown.js'
+import { onCotChange, pruneStaleEntities } from '../utils/cotStore.js'
+import { getCotSnapshotOpts } from '../utils/cotSnapshot.js'
+import {
+  notifySubscribersForEntity,
+  notifySubscribersRemove,
+} from '../utils/cotSubscribers.js'
+import { COT_PRUNE_INTERVAL_MS } from '../utils/constants.js'
+
+let pruneTimer = null
+let offChange = () => {}
+
+export default defineNitroPlugin(() => {
+  offChange = onCotChange((changeEvent, payload) => {
+    if (changeEvent === 'update' && payload?.entity) {
+      notifySubscribersForEntity('update', { entity: payload.entity }, payload.entity).catch(() => {})
+    }
+    else if (changeEvent === 'remove' && payload?.id) {
+      notifySubscribersRemove(payload.id).catch(() => {})
+    }
+  })
+
+  pruneTimer = setInterval(() => {
+    pruneStaleEntities(getCotSnapshotOpts()).catch(() => {})
+  }, COT_PRUNE_INTERVAL_MS)
+
+  registerCleanup(() => {
+    offChange()
+    if (pruneTimer) clearInterval(pruneTimer)
+    pruneTimer = null
+  })
+})

server/plugins/trackingFeed.js

@@ -0,0 +1,7 @@
+import { registerCleanup } from '../utils/shutdown.js'
+import { startTrackingFeed, stopTrackingFeed } from '../utils/trackingFeed.js'
+
+export default defineNitroPlugin(() => {
+  startTrackingFeed()
+  registerCleanup(stopTrackingFeed)
+})