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/api/cameras.get.js

@@ -1,19 +1,15 @@
 import { getDb } from '../utils/db.js'
 import { requireAuth } from '../utils/authHelpers.js'
 import { getActiveSessions } from '../utils/liveSessions.js'
-import { getActiveEntities } from '../utils/cotStore.js'
 import { rowToDevice, sanitizeDeviceForResponse } from '../utils/deviceUtils.js'
 
 export default defineEventHandler(async (event) => {
   requireAuth(event)
-  const config = useRuntimeConfig()
-  const ttlMs = Number(config.cotTtlMs ?? 90_000) || 90_000
-  const [db, sessions, cotEntities] = await Promise.all([
+  const [db, sessions] = await Promise.all([
     getDb(),
     getActiveSessions(),
-    getActiveEntities(ttlMs),
   ])
   const rows = await db.all('SELECT id, name, device_type, vendor, lat, lng, stream_url, source_type, config FROM devices ORDER BY id')
   const devices = rows.map(rowToDevice).filter(Boolean).map(sanitizeDeviceForResponse)
-  return { devices, liveSessions: sessions, cotEntities }
+  return { devices, liveSessions: sessions }
 })