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/nuxt/KestrelMap.spec.js

@@ -75,4 +75,12 @@ describe('KestrelMap', () => {
     expect(wrapper.props('pois')).toHaveLength(1)
     expect(wrapper.props('canEditPois')).toBe(false)
   })
+
+  it('includes CoT layer toggles and supercluster layer', async () => {
+    const componentPath = resolve(__dirname, '../../app/components/KestrelMap.vue')
+    const source = readFileSync(componentPath, 'utf-8')
+    expect(source).toContain('cot-layer-toggles')
+    expect(source).toContain('cotMapLayer')
+    expect(source).toContain('syncCotLayer')
+  })
 })