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.

src/data/dataCredits.js

@@ -293,6 +293,16 @@ export const DATA_CREDITS = [
       '<a href="https://www2.gov.bc.ca/gov/content/data/open-data/open-government-licence-bc" target="_blank" rel="noopener">Open Government Licence – British Columbia</a>. ' +
       'Some cameras are supplied by partners (TransLink, the City of Vancouver, the City of Surrey, Parks Canada and others); each names its provider in the CCTV panel.',
   },
+  {
+    key: 'wsdot-cctv',
+    html:
+      'CCTV cameras &amp; frames (Washington State): ' +
+      '<a href="https://wsdot.wa.gov/" target="_blank" rel="noopener">Washington State Department of Transportation</a> ' +
+      '(<a href="https://wsdot.com/travel/real-time/cameras" target="_blank" rel="noopener">Travel Center</a>), ' +
+      'used per the ' +
+      '<a href="https://wsdot.wa.gov/about/policies/travel-information-disclaimer" target="_blank" rel="noopener">WSDOT travel information disclaimer</a> ' +
+      '(low-volume public feed; catalog cached, frames proxied on demand)',
+  },
   {
     key: 'tallinn-cctv',
     html: