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]>

server/providers/shipwrecks.js

@@ -0,0 +1,151 @@
+import {
+  EMODNET_WFS_URL,
+  WIKIDATA_QUERY,
+  mergeShipwreckRecords,
+  normalizeEmodnetFeatures,
+  normalizeWikidataResults,
+} from '../../src/layers/shipwrecks/records.js';
+import { coalesceProxyRequest, readResponseJsonCapped } from './common/http.js';
+import { clientKey, makeRateLimiter } from './common/rate-limit.js';
+
+const MIB = 1024 * 1024;
+/** EMODnet republishes the wreck layer about once a year; Wikidata daily at most. */
+const REFRESH_MS = 24 * 60 * 60 * 1000;
+/** A failed refresh keeps serving the last snapshot this long, marked stale. */
+const STALE_MAX_MS = 7 * REFRESH_MS;
+// Only the columns the card uses; ship_char/obj_desc histories can name people
+// and are not read beyond a short vessel type.
+const EMODNET_PROPERTIES = [
+  'source_id',
+  'country',
+  'name',
+  'least_depth',
+  'depth_prec',
+  'loc_prec',
+  'sink_context',
+  'sink_yr',
+  'dating',
+  'period',
+  'statutory',
+  'ship_char',
+  'obj_type',
+  'artefacts',
+  'source_inf',
+  'website1',
+  'point_info',
+  'the_geom',
+].join(',');
+const EMODNET_URL = `${EMODNET_WFS_URL}&propertyName=${EMODNET_PROPERTIES}`;
+const WIKIDATA_URL =
+  'https://query.wikidata.org/sparql?format=json&query=' +
+  encodeURIComponent(WIKIDATA_QUERY);
+// Wikimedia asks automated clients to name themselves.
+const USER_AGENT =
+  "God's Eye View shipwrecks layer (https://github.com/bilawalsidhu/gods-eye-view)";
+
+/** Fixed-origin, cached EMODnet + Wikidata shipwreck snapshot for dev and preview. */
+export function shipwrecksProxy({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+  now = () => Date.now(),
+} = {}) {
+  let snapshot = null;
+  const inFlight = new Map();
+  const allow = makeRateLimiter({ windowMs: 60_000, max: 30, globalMax: 600 });
+
+  async function upstreamJson(url, maxBytes) {
+    const signal = AbortSignal.timeout(90_000);
+    const response = await fetchImpl(url, {
+      signal,
+      redirect: 'error',
+      headers: { 'User-Agent': USER_AGENT, Accept: 'application/json' },
+    });
+    if (!response.ok) {
+      await response.body?.cancel();
+      throw new Error('upstream_unavailable');
+    }
+    return readResponseJsonCapped(response, maxBytes, signal);
+  }
+
+  async function fetchEmodnet() {
+    const records = normalizeEmodnetFeatures(
+      await upstreamJson(EMODNET_URL, 32 * MIB),
+    );
+    if (!records.length) throw new Error('invalid_emodnet_layer');
+    return records;
+  }
+
+  async function fetchWikidata() {
+    return normalizeWikidataResults(await upstreamJson(WIKIDATA_URL, 16 * MIB));
+  }
+
+  /** One source failing still serves the other; both failing is an error. */
+  async function load() {
+    const [emodnet, wikidata] = await Promise.allSettled([
+      fetchEmodnet(),
+      fetchWikidata(),
+    ]);
+    if (emodnet.status === 'rejected' && wikidata.status === 'rejected')
+      throw new Error('shipwrecks_unavailable');
+    const records = mergeShipwreckRecords(
+      emodnet.status === 'fulfilled' ? emodnet.value : [],
+      wikidata.status === 'fulfilled' ? wikidata.value : [],
+    );
+    return {
+      fetchedAt: now(),
+      sources: {
+        emodnet: emodnet.status === 'fulfilled',
+        wikidata: wikidata.status === 'fulfilled',
+      },
+      records,
+    };
+  }
+
+  async function acquire() {
+    if (snapshot && now() - snapshot.fetchedAt < REFRESH_MS)
+      return { value: snapshot, stale: false };
+    try {
+      const { promise } = coalesceProxyRequest(inFlight, 'snapshot', load);
+      snapshot = await promise;
+      return { value: snapshot, stale: false };
+    } catch (error) {
+      if (snapshot && now() - snapshot.fetchedAt <= STALE_MAX_MS)
+        return { value: snapshot, stale: true };
+      throw error;
+    }
+  }
+
+  async function handler(req, res) {
+    const json = (status, value, stale = false) => {
+      if (res.destroyed) return;
+      res.writeHead(status, {
+        'Content-Type': 'application/json',
+        'Cache-Control': 'no-store',
+        ...(status === 405 ? { Allow: 'GET' } : {}),
+        ...(status === 429 ? { 'Retry-After': '60' } : {}),
+        ...(stale ? { 'X-Data-Stale': 'true' } : {}),
+      });
+      res.end(JSON.stringify(value));
+    };
+    if (req.method !== 'GET') return json(405, { error: 'method_not_allowed' });
+    const path = (req.url || '/').split('?')[0];
+    if (path !== '/' && path !== '')
+      return json(404, { error: 'unknown_route' });
+    if (!allow(clientKey(req))) return json(429, { error: 'rate_limited' });
+    try {
+      const { value, stale } = await acquire();
+      json(200, stale ? { ...value, stale: true } : value, stale);
+    } catch {
+      json(502, { error: 'shipwrecks_unavailable' });
+    }
+  }
+
+  return {
+    name: 'shipwrecks',
+    configureServer({ middlewares }) {
+      middlewares.use('/api/shipwrecks', handler);
+    },
+    configurePreviewServer({ middlewares }) {
+      middlewares.use('/api/shipwrecks', handler);
+    },
+  };
+}