Map: pin 511NY camera feeds as tiles on the map (#183)

Clicking a camera's snapshot pins a 192x108 tile anchored at the camera --
the live HLS stream when the camera has one (hls.js; Safari native), else the
snapshot refreshed every 60s, falling back to the snapshot if the stream dies.
Up to 6 pins, oldest dropped. Players exist only while the DOT Cameras overlay
is on, so hiding it stops every stream.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/package.json

@@ -13,6 +13,7 @@
     "react": "^18.3.0",
     "react-dom": "^18.3.0",
     "firebase": "^10.12.0",
+    "hls.js": "^1.5.0",
     "leaflet": "^1.9.4",
 "react-leaflet": "^4.2.1",
     "react-markdown": "^9.0.1"