feat(cctv): WSDOT highway camera source pack (Washington State)

Adds Washington State's highway cameras as a keyless source pack, from the
Esri JSON layer WSDOT's own Travel Center map consumes
(data.wsdot.wa.gov/travelcenter/Cameras.json, ~1,700 point features).
Closes #624.

- Geometry arrives in EPSG:3857; converted to WGS84 on load and bounded to
  a Washington bounding box.
- Only frames on WSDOT's own images.wsdot.wa.gov host are registered — the
  catalog also lists ~70 partner cameras (Oregon DOT, City of Seattle,
  lodges, airports) whose own terms apply; those are skipped rather than
  proxied. 1,630 cameras survive the filters against the live feed.
- CompassDirection letters (N/E/S/W) give a high-confidence heading; the
  majority `B` ("both directions") rows carry no single facing and use the
  shared id-hash fallback at low confidence, with the usual two pose
  personalities.
- The feed body carries Windows-1252 bytes (en-dashes in titles) with no
  charset declaration, so it is decoded explicitly before parsing.
- WSDOT's layer metadata marks the feed "low volume": the 15-minute catalog
  cache and per-request frame fetches respect that, frames are never stored
  or redistributed, and the WSDOT credit is registered in the attribution
  popover. A keyed WSDOT Traveler Information API serves the same population
  for higher-volume use and is deliberately not required.
- Defaults: 250 cameras nearest Seattle and Spokane; CCTV_WSDOT_MAX_SOURCES
  changes the cap, CCTV_WSDOT_ENABLED=0 turns the pack off.
- Tests: Mercator conversion against a real layer feature, official-host and
  malformed-row filtering, compass mapping and both pose personalities,
  cp1252 decoding, env cap, upstream-failure fallback.

server/providers/cctv/constants.js

@@ -244,6 +244,24 @@ export const DELDOT_ANCHORS = [
   { lat: 39.1582, lon: -75.5244 }, // Dover (Kent)
   { lat: 38.6906, lon: -75.3877 }, // Georgetown (Sussex)
 ];
+
+/** WSDOT Travel Center cameras (Washington State): keyless Esri JSON on the
+ * official open-data host — ~1,700 point features in EPSG:3857 (Web Mercator),
+ * ETag/Last-Modified served. WSDOT's metadata marks the feed "low volume" use,
+ * which the 15-minute catalog cache respects. */
+export const WSDOT_CAMERAS_URL =
+  'https://data.wsdot.wa.gov/travelcenter/Cameras.json';
+/** Only frames on WSDOT's own image host are registered; the catalog also
+ * lists ~70 partner cameras (Oregon DOT, City of Seattle, lodges, airports)
+ * whose own terms apply. */
+export const WSDOT_IMAGE_ORIGIN = 'https://images.wsdot.wa.gov/';
+export const DEFAULT_WSDOT_MAX_SOURCES = 250;
+/** Prioritization anchors: downtown Seattle and Spokane. */
+export const WSDOT_ANCHORS = [
+  { lat: 47.6062, lon: -122.3321 }, // Seattle
+  { lat: 47.6588, lon: -117.426 }, // Spokane
+];
+
 /** Camera CATALOGS change rarely; 15 min keeps multi-megabyte upstream list refetches (Austin rows.json + 4 Caltrans districts + TfL + Ontario 511) infrequent. Frames are fetched per-request and are unaffected. */
 export const CCTV_SOURCE_CACHE_MS = 15 * 60 * 1000;
 /** Per-provider catalog-fetch timeout. Bounds the worst-case refresh so one