Weather backend: NWS active alerts + nearest-METAR wind, cached (Refs #237)

GET /weather/alerts — api.weather.gov/alerts/active for settings.nws_area,
sent with the NWS-required User-Agent, cached weather_alerts_ttl_s (90 s)
with single-flight refresh. Zone-based alerts (geometry null) get their
polygons from affectedZones (24 h zone cache, api.weather.gov/zones/ only);
any still unresolved are returned in zone_only, never dropped. Failed
refresh keeps last-good data + error + fetched_at; a payload where no
feature parses is a schema-change error. Optional bbox filter.

GET /weather/wind — nearest METAR (aviationweather.gov /api/data/metar,
bbox query) within 75 km, cached 5 min per 0.5-degree cell; VRB wind and
stale reports flagged; available:false with a reason otherwise.

Both behind require_service_or_firebase_token like /traffic.

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

drb-c2-core/.env.example

@@ -31,6 +31,10 @@ NY511_API_KEY=
 NY511_API_BASE=
 # Ontario 511 developer key (camera provider "ontario511"; providers default OFF)
 ONTARIO511_API_KEY=
+# NWS weather alerts / METAR wind (server-26#237). NWS requires app name + contact in the User-Agent
+NWS_USER_AGENT=DRB (you@example.com)
+# Comma list of NWS state/marine area codes served
+NWS_AREA=NY
 
 # OpenAI — for transcription (Whisper), intelligence extraction, embeddings, and summaries
 OPENAI_API_KEY=