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/catalog.js

@@ -18,6 +18,7 @@ import {
   loadNswSourcesFromOpenData,
   loadCalgarySourcesFromOpenData,
   loadDelDOTSourcesFromOpenData,
+  loadWsdotSourcesFromOpenData,
 } from './sources.js';
 
 /** Env kill switch: unset or anything but "0" means enabled. */
@@ -92,6 +93,11 @@ const LIVE_PACKS = [
     enabled: () => envEnabled('CCTV_DELDOT_ENABLED'),
     load: loadDelDOTSourcesFromOpenData,
   },
+  {
+    name: 'wsdot',
+    enabled: () => envEnabled('CCTV_WSDOT_ENABLED'),
+    load: loadWsdotSourcesFromOpenData,
+  },
 ];
 /**
  * Load CCTV sources from a local JSON file (CCTV_SOURCES_FILE env or default).