Merge origin/i18n-spanish: whole-interface translation meets KartaView

This branch moved twice at once: upstream merged KartaView (#1121, a
third keyless street-level provider sharing a new lineCoverage.js), and
the remote i18n-spanish gained the whole-interface translation work
(1993 catalog entries, translateKnown, data-i18n-runtime, the unmarked-
string detector in npm run i18n) built on the Street View merge.

Integration keeps the remote's mechanisms and re-adds KartaView on top:

- presentMeta: remote's translateHint for coverage hints, plus the
  KartaView count line as its own literal tn pair (Russian plurals need
  the noun inside the template; keyed off coverageLabel.noun with the
  sequences pair as the default).
- uiState: upstream's highlightsSequence legend gate (KartaView's lines
  do not highlight) with t('Selected').
- layer-panels.html: remote's data-i18n/data-i18n-runtime hooks plus the
  sl-since-note wiring KartaView's upload-date SINCE note needs.
- kartaview viewer: the photo-navigation aria-label and img alt go
  through t(), as the remote's unmarked-string detector requires.
- catalogs: remote's 1987-entry base (its refined keys supersede this
  branch's earlier Street View wording) plus the KartaView entries:
  coverage hints, the upload-date note, the streets count line (with
  Russian one/few/many/other forms) and the viewer strings.

npm run i18n: complete, no unmarked strings. npm test: 6520/6522 (the
one failure is the pre-existing environmental OPENAI_API_KEY leak in
devFreshDotenv). Build passes.

CHANGELOG.md

@@ -21,7 +21,9 @@
   switch in the Visual Presets dock, then the browser language; English stays
   the default and the fallback. `npm run i18n`, also run by `npm test`, fails on
   missing, unused or broken translations. Built on the i18n foundation by
-  @meirm (#601), with the Russian catalog started from #312.
+  @meirm (#601), with the Russian catalog started from #312. It also fails on UI text that is
+  not marked at all, so the whole interface, including surfaces added after
+  the original extraction, is translated (1,679 messages).
 
 - Treat explicitly current, complete empty vessel coverage as a successful update,
   clearing obsolete contacts while retaining stale or incomplete snapshots.