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

test/unit/cotMapLayer.spec.js

@@ -0,0 +1,46 @@
+import { describe, it, expect } from 'vitest'
+import {
+  entitiesToFeatures,
+  getCotClusters,
+  loadCotCluster,
+} from '../../app/utils/cotMapLayer.js'
+
+function makeEntities(n, centerLat = 37.7, centerLng = -122.4) {
+  return Array.from({ length: n }, (_, i) => ({
+    id: `ICAO.${i}`,
+    lat: centerLat + (i % 10) * 0.01,
+    lng: centerLng + Math.floor(i / 10) * 0.01,
+    type: 'a-f-A-C-F',
+    label: `AC${i}`,
+  }))
+}
+
+describe('cotMapLayer', () => {
+  it('converts entities to GeoJSON points', () => {
+    const features = entitiesToFeatures([
+      { id: 'ICAO.1', lat: 37.7, lng: -122.4, type: 'a-f-A-C-F' },
+      { id: 'bad', lat: 'x', lng: 0 },
+    ])
+    expect(features).toHaveLength(1)
+    expect(features[0].geometry.coordinates).toEqual([-122.4, 37.7])
+    expect(features[0].properties.entity.id).toBe('ICAO.1')
+  })
+
+  it('clusters dense tracks at low zoom', () => {
+    loadCotCluster(makeEntities(50))
+    const view = { west: -123, south: 37, east: -122, north: 38, zoom: 6 }
+    const clusters = getCotClusters(view)
+    const clusterCount = clusters.filter(f => f.properties?.cluster).length
+    const pointCount = clusters.filter(f => !f.properties?.cluster).length
+    expect(clusterCount).toBeGreaterThan(0)
+    expect(clusterCount + pointCount).toBeLessThan(50)
+  })
+
+  it('shows individual markers at high zoom', () => {
+    loadCotCluster(makeEntities(20))
+    const view = { west: -123, south: 37, east: -122, north: 38, zoom: 15 }
+    const clusters = getCotClusters(view)
+    expect(clusters.every(f => !f.properties?.cluster)).toBe(true)
+    expect(clusters).toHaveLength(20)
+  })
+})