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

app/composables/useCameras.js

@@ -1,6 +1,6 @@
 /** Fetches devices + live sessions; polls when tab visible. */
 const POLL_MS = 1500
-const EMPTY_RESPONSE = Object.freeze({ devices: [], liveSessions: [], cotEntities: [] })
+const EMPTY_RESPONSE = Object.freeze({ devices: [], liveSessions: [] })
 
 export function useCameras(options = {}) {
   const { poll: enablePoll = true } = options
@@ -12,7 +12,6 @@ export function useCameras(options = {}) {
 
   const devices = computed(() => Object.freeze([...(data.value?.devices ?? [])]))
   const liveSessions = computed(() => Object.freeze([...(data.value?.liveSessions ?? [])]))
-  const cotEntities = computed(() => Object.freeze([...(data.value?.cotEntities ?? [])]))
   const cameras = computed(() => Object.freeze([...devices.value, ...liveSessions.value]))
 
   const pollInterval = ref(null)
@@ -37,5 +36,5 @@ export function useCameras(options = {}) {
   })
   onBeforeUnmount(stopPolling)
 
-  return Object.freeze({ data, devices, liveSessions, cotEntities, cameras, refresh, startPolling, stopPolling })
+  return Object.freeze({ data, devices, liveSessions, cameras, refresh, startPolling, stopPolling })
 }