feat(layers): add shipwrecks layer (EMODnet + Wikidata)

A new Events layer maps shipwrecks with a card per wreck:
- EMODnet Human Activities heritage shipwrecks (about 6,500 in European
  waters, CC BY 4.0), skipping rows taken from wrecksite.eu.
- Wikidata shipwrecks with a Wikipedia article plus sinking events
  (CC0); an event folds into its ship for the date and death toll.
- A same-origin /api/shipwrecks proxy refreshes once a day and serves
  the last snapshot as stale for up to a week.

Markers are a boat icon coloured by era and sized by deaths; four era
chips filter the layer. The card follows the air-accidents layout
(deaths first). Text that names people is dropped; victims appear as
a count only.

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

scripts/format-scope.json

@@ -1267,5 +1267,9 @@
   "src/voice/geminiTextChat.js",
   "src/voice/panelLayout.js",
   "src/voice/textChat.js",
-  "src/voice/textProtocol.js"
+  "src/voice/textProtocol.js",
+  "src/layers/shipwrecks/records.test.mjs",
+  "src/layers/shipwrecks/cards.test.mjs",
+  "src/layers/shipwrecks/eras.test.mjs",
+  "src/data/shipwrecksProxy.test.mjs"
 ]