feat: Wildlife Sightings layer from iNaturalist and Acartia

Recent community wildlife observations, as a new Wildlife group in the
layer panel.

- Server: keyless iNaturalist proxy (v2 observations with only the
  projected fields; undocumented v1 UTFGrid density tiles, decoded on the
  server) sharing one paced queue (burst 4, ~1/s, 60/min, 8,000/day budget,
  up to four in flight), in-memory caches and upstream-only cooldowns;
  Acartia Salish Sea marine-mammal feed rounded to 0.01 degrees with
  comments dropped.
- Layer: grid counts drawn as a soft view-ranked density glow; real sampled
  sightings as taxon badges at their true positions with ambient photo
  thumbnails and labels; obscured records stay privacy cells; a clicked
  sighting stays pinned through camera moves and refreshes.
- Anchored photo card per selection with the single iNaturalist link;
  attribution in the layer row and the Data attribution popover.
- Filters (CONFIRMED, taxa presets) round-trip in share links with token 9.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/data/layerState.js

@@ -312,6 +312,23 @@ const OPTION_GROUPS = Object.freeze({
       high: 'h',
     }),
   ]),
+  'wildlife-sightings': Object.freeze([
+    booleanOption('confirmed', 'c', false),
+    enumOption(
+      'taxa',
+      't',
+      'all',
+      ['all', 'Aves', 'Mammalia', 'whales', 'Insecta', 'Plantae'],
+      {
+        all: 'a',
+        Aves: 'b',
+        Mammalia: 'm',
+        whales: 'w',
+        Insecta: 'i',
+        Plantae: 'p',
+      },
+    ),
+  ]),
   traffic: Object.freeze([
     enumOption('roadMode', 'r', null, ['tomtom', 'osm', 'hybrid'], {
       tomtom: 't',
@@ -733,6 +750,12 @@ export const LAYER_STATE_REGISTRY = Object.freeze([
     disposition: 'enabled+options',
     optionOwner: 'weather-satellite',
   }),
+  Object.freeze({
+    id: 'wildlife-sightings',
+    token: '9',
+    disposition: 'enabled+options',
+    optionOwner: 'wildlife-sightings',
+  }),
   Object.freeze({
     id: 'wind',
     token: 'k',