fix(shipwrecks): small row and query fixes: era counts in one pass, pickers list only years with a wreck, no Portuguese default

- The legend counted each era twice, scanning every record eight times per
  row refresh; it now counts once.
- Each year picker listed every year from the oldest dated wreck (well over
  a thousand entries); it lists the years that have a wreck, plus the chosen
  ends.
- Labels fell back to Portuguese and links to Portuguese Wikipedia while the
  app ships 11 locales: labels now fall back through the app's languages
  after English, and a wreck with no English article links its Wikidata
  item, which lists the article in every language.

docs/CURRENT-STATE.md

@@ -178,7 +178,7 @@ cull GhostMaps uses, sized by deaths (a bigger toll draws on top) and coloured
 by era (a legend under the row): before 1900
 (ancient wrecks dated only by period count here), 1900–1945, after 1945, and
 date unknown. A period filter under the row picks a start year and an end year
-side by side (two pickers over the years in the data; a reversed pair is
+side by side (two pickers over the years that have a wreck; a reversed pair is
 stored swapped); undated wrecks show only when every year
 is selected. The filter is session-only (not in the share link). Clicking a marker opens a `stateless` card: deaths and
 survivors first, then the sinking date or year (or the archaeological dating) and