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/utils/db.js

@@ -8,7 +8,7 @@ import { registerCleanup } from './shutdown.js'
 const requireFromRoot = createRequire(join(process.cwd(), 'package.json'))
 const { DatabaseSync } = requireFromRoot('node:sqlite')
 
-const SCHEMA_VERSION = 4
+const SCHEMA_VERSION = 6
 const DB_BUSY_TIMEOUT_MS = 5000
 
 let dbInstance = null
@@ -59,6 +59,20 @@ const SCHEMA = {
     source_type TEXT NOT NULL DEFAULT 'mjpeg',
     config TEXT
   )`,
+  alpr_nodes: `CREATE TABLE IF NOT EXISTS alpr_nodes (
+    osm_id INTEGER PRIMARY KEY,
+    lat REAL NOT NULL,
+    lng REAL NOT NULL,
+    manufacturer TEXT,
+    direction INTEGER,
+    tags TEXT NOT NULL,
+    fetched_at TEXT NOT NULL
+  )`,
+  alpr_nodes_index: 'CREATE INDEX IF NOT EXISTS idx_alpr_lat_lng ON alpr_nodes(lat, lng)',
+  alpr_tiles: `CREATE TABLE IF NOT EXISTS alpr_tiles (
+    tile_key TEXT PRIMARY KEY,
+    fetched_at TEXT NOT NULL
+  )`,
 }
 
 const getDbPath = () => {
@@ -118,6 +132,19 @@ const migrateToV4 = async (run, all) => {
   await run('ALTER TABLE users ADD COLUMN cot_password_hash TEXT')
 }
 
+const migrateToV5 = async (run, all) => {
+  const tables = await all('SELECT name FROM sqlite_master WHERE type=\'table\' AND name=\'alpr_nodes\'')
+  if (tables.length > 0) return
+  await run(SCHEMA.alpr_nodes)
+  await run(SCHEMA.alpr_nodes_index)
+}
+
+const migrateToV6 = async (run, all) => {
+  const tables = await all('SELECT name FROM sqlite_master WHERE type=\'table\' AND name=\'alpr_tiles\'')
+  if (tables.length > 0) return
+  await run(SCHEMA.alpr_tiles)
+}
+
 const runMigrations = async (run, all, get) => {
   const version = await getSchemaVersion(get)
   if (version >= SCHEMA_VERSION) return
@@ -133,6 +160,14 @@ const runMigrations = async (run, all, get) => {
     await migrateToV4(run, all)
     await setSchemaVersion(run, 4)
   }
+  if (version < 5) {
+    await migrateToV5(run, all)
+    await setSchemaVersion(run, 5)
+  }
+  if (version < 6) {
+    await migrateToV6(run, all)
+    await setSchemaVersion(run, 6)
+  }
 }
 
 const initDb = async (db, run, all, get) => {
@@ -149,6 +184,9 @@ const initDb = async (db, run, all, get) => {
   await run(SCHEMA.sessions)
   await run(SCHEMA.pois)
   await run(SCHEMA.devices)
+  await run(SCHEMA.alpr_nodes)
+  await run(SCHEMA.alpr_nodes_index)
+  await run(SCHEMA.alpr_tiles)
 
   if (!testPath) {
     // Bootstrap admin user on first run