feat(layers): add FAA drone restrictions airspace layer

Show US prohibited and restricted special-use airspace from the keyless
FAA SUA FeatureServer as an off-by-default Infrastructure layer, with
share-link token 3 and an informational-only disclaimer.

DATA_SOURCES.md

@@ -35,6 +35,7 @@ How to read this:
 | **NASA GIBS** (WMTS tiles + Worldview Snapshots) and **NASA CMR** (granule catalog) | Recent Imagery layer: HLS S30/L30 (Sentinel-2, Landsat 8/9) and VIIRS true-colour tiles draped on the map, per-day thumbnails and PNG exports; the HLS granule catalog (dates, cloud, footprints) for a selected box | U.S. public domain (NASA data); keyless, browser-direct (CORS `*`); no bulk use — one 30-day catalog query per box, tiles bounded to the box, six tile requests in flight | "We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS)." — [gibs.earthdata.nasa.gov](https://gibs.earthdata.nasa.gov), [HLS](https://lpdaac.usgs.gov/products/hlss30v002/) |
 | **NIFC WFIGS** (Wildland Fire Interagency Geospatial Services, ArcGIS feature service) | Fire Perimeters layer: current interagency wildfire incident perimeters, containment, and incident facts | U.S. public domain (interagency wildland-fire data published through the [NIFC Open Data portal](https://data-nifc.opendata.arcgis.com/)); fetched keyless through `/api/fire-perimeters` (5-minute server cache) with `exceededTransferLimit` paging | "Wildfire perimeters: National Interagency Fire Center (WFIGS)" |
 | **InciWeb** (inciweb.wildfire.gov)                                    | Per-incident "InciWeb ↗" card links to official incident pages (narratives, evacuation/closure notices) | U.S. government public incident information. Links are matched best-effort by incident name and state, with incident page origin and update times checked on selection. Same-origin `/api/fire-perimeters/inciweb` routes cache the catalog for 1 hour and publication metadata for 30 minutes; linked pages remain InciWeb content | "Incident information: InciWeb (inciweb.wildfire.gov)" |
+| **FAA Special Use Airspace** (`services6.arcgis.com` FeatureServer `Special_Use_Airspace`) | Drone Restrictions layer: US prohibited (P) and restricted (R) special-use airspace polygons, altitude limits, times of use, and controlling agency | U.S. public domain (FAA aeronautical data published through the [FAA AIS Open Data portal](https://adds-faa.opendata.arcgis.com/)); fetched keyless through `/api/drone-airspace` (1-hour server cache). Informational only — not a substitute for official UAS flight-planning tools | "Drone restrictions: FAA Special Use Airspace" |
 | **OpenFreeMap / OpenMapTiles** | Vector tiles | OpenStreetMap data under ODbL 1.0 | OpenFreeMap © OpenMapTiles |
 | **Overture Maps Foundation** | Military area names pack | [ODbL 1.0](https://opendatacommons.org/licenses/odbl/1-0/) | Overture Maps Foundation |
 | **TomTom Traffic API** (flow vector tiles)                            | Traffic roads and live congestion (optional, BYOK)                                                                     | [TomTom for Developers terms](https://docs.tomtom.com/legal/terms-and-conditions) (proprietary, your own key; free tier currently 200K tile requests/month — see [current pricing](https://docs.tomtom.com/pricing/))                                                                                                                                                       | "Traffic flow data © TomTom" — registered when live mode activates                                                                          |
@@ -98,6 +99,7 @@ The optional Local ADS-B layer and the broadcast-FM receiver use radio you recei
 - **Routing (OSRM / FOSSGIS).** `/api/route` proxies the public OSRM instances FOSSGIS e.V. runs for the OpenStreetMap community (car, bike, foot profiles). They are keyless and intended for fair, interactive use — the proxy rate-limits clients (60/min, 200/min total), caps route span and response size, caches each route for 10 minutes, and identifies itself in the User-Agent. Heavy or automated use must run its own OSRM. Routes are computed from OpenStreetMap data (ODbL); the Directions layer and voice routes never redistribute them. A route the router cannot find is reported as such; the Directions layer draws nothing in that case, and voice routes fall back to a clearly labeled straight line.
 - **Re:Earth Terrain.** Keyless (no API key). Used two ways: (1) `src/mapStackController.js` swaps in a `Cesium.CesiumTerrainProvider` pointed at Re:Earth's `cesium-mesh/ellipsoid` quantized-mesh endpoint for globe stacks without a Cesium ion token (e.g. OSM), replacing a flat `EllipsoidTerrainProvider`; falls back to the flat provider if the endpoint can't be reached. (2) The server-side `/api/terrain/heights` proxy (disk-cached, serve-stale) resolves per-point ellipsoidal ground height for entity placement. Both are best-effort with a keyless-safe fallback (bundled EGM96 geoid math) if Re:Earth is unreachable.
 - **OSRM on the FOSSGIS routing servers.** Keyless (no API key). Every route is requested by a person: clicking A and B in the Directions layer, or a voice "route from A to B". The server-side `/api/route` proxy sends an identifying `User-Agent`, pins the upstream host, accepts 2-12 coordinates, rejects any leg over 600 km or a total over 2,500 km, caps the buffered response at 8 MB, times the upstream out at 12 s, rate-limits per client, caches each route for 10 minutes, and coalesces identical requests that are in flight at the same time. Turn-by-turn maneuvers are asked for only when a caller wants them (`steps=1`), so the callers that do not read them send the smaller request. The "fix the map" link the policy asks for is in the Data attribution popover beside the OpenStreetMap credit.
+- **FAA Special Use Airspace.** Keyless. `/api/drone-airspace` queries the public FAA AIS FeatureServer for prohibited (P) and restricted (R) zones only — not MOAs, TFRs or other SUA types — with simplified geometry, a body cap, paging, a one-hour cache and stale-on-error. The layer is US coverage, informational only, and is not a substitute for B4UFLY, LAANC or a preflight briefing. Data is fetched at request time and never stored or redistributed. US government public domain; courtesy attribution is registered in the Data attribution popover.
 - **Mapped installations.** OpenFreeMap military polygons use a bundled Overture/OSM name index; wide views show named points. Optional operator-configured Overpass and explicit Google Places searches keep their own source paths. Mapped data does not establish current activity or complete coverage.
 - **Place search.** Named-place fly-to uses Google Geocoding when a Maps key is configured, then Photon's public instance, then `/api/geocode` (Nominatim search) when neither answers. `/api/geocode` uses the shared Nominatim forward-search queue at no more than one request per second, sends an identifying `User-Agent` and `Referer`, caches answers for five minutes, shares one upstream call between identical searches already in flight, bounds the queue so a burst is refused rather than held, and drops a queued search whose caller has given up. It asks for one result per search and is not used for systematic or bulk queries.
 - **Cockpit regional briefing.** `/api/regional-brief` rounds aircraft coordinates into 0.1° cache cells, caches results for five minutes, and resolves physical regions from bundled public-domain Natural Earth polygons without reverse-geocoding requests. Google News RSS is queried with the resolved locality/region first; GDELT is used only when that RSS query fails or is empty. Google's published Google News terms restrict that source to personal, noncommercial use, so commercial deployments must disable/replace it or obtain separate permission; GDELT permits commercial dataset use with citation. The Data attribution popover identifies the active headline sources; article links retain publisher attribution. Headlines are location-query matches, not verified incidents, risk rankings, or evidence that a location is safe. Empty, partial, stale, and unavailable source states remain distinct. Open-Meteo supplies current conditions independently of the news source. `WX OFF` disables cockpit weather rendering only; the Local Info briefing still fetches its source-backed weather values and displays the required linked Open-Meteo credit.