Merge upstream/main: KartaView provider meets i18n

Upstream's KartaView PR (#1121) extracted the Mapillary coverage engine
into a shared lineCoverage.js and made the panel wording
provider-specific (coverage noun/action, SINCE upload-date note,
highlightsSequence legend gate), again in the regions this branch
localizes.

- mapillary/coverage.js: taken as upstream's thin re-export of the new
  lineCoverage.js; the generic too-high hint stays msg()-marked, now in
  lineCoverage.js where the default lives.
- kartaview/policy.js: coverage hints (tooHigh, noCoverage) marked as
  msg() data so they translate like every other coverage hint; thrown
  error messages stay English, matching the Mapillary precedent.
- presentMeta: KartaView counts streets, and Russian plurals need the
  noun inside the template, so the count line gets its own literal tn
  pair keyed off coverageLabel.noun, falling back to the sequences pair;
  upstream's noun/action data contract is untouched.
- uiState legend: upstream highlightsSequence gate with t('Selected');
  sinceNote localized with a {names} placeholder.
- layer-panels.html: sl-since-note wiring kept, data-i18n hooks kept.
- CHANGELOG: both sides kept. es/ru: 4 new keys each.

npm run i18n complete (953 messages each); npm test 6504/6506 (the one
failure is the pre-existing environmental OPENAI_API_KEY leak in
devFreshDotenv, unrelated); build passes.

src/i18n/locales/es.json

@@ -956,6 +956,14 @@
   "Open {names} at the centre of the view": "Abre {names} en el centro de la vista",
   "Zoom in to a street to open {names} here": "Acércate a una calle para abrir {names} aquí",
   "OPEN STREET VIEW": "ABRIR STREET VIEW",
+  "zoom in to see KartaView coverage": "acércate para ver la cobertura de KartaView",
+  "no KartaView photos in view": "no hay fotos de KartaView a la vista",
+  "{names}: by upload date": "{names}: por fecha de subida",
+  "{n} streets in view · click a line for its nearest photo": {
+    "one": "{n} calle a la vista · haz clic en una línea para su foto más cercana",
+    "many": "{n} calles a la vista · haz clic en una línea para su foto más cercana",
+    "other": "{n} calles a la vista · haz clic en una línea para su foto más cercana"
+  },
   "Camera follows view: move the globe camera wherever the street-level view looks": "La cámara sigue la vista: mueve la cámara del globo hacia donde mira la vista a pie de calle",
   "Camera follow needs the Google 3D map: choose Google 3D under MAP SOURCE": "Seguir con la cámara requiere el mapa Google 3D: elige Google 3D en FUENTE DEL MAPA",
   "Switch a provider on to draw its coverage.": "Activa un proveedor para dibujar su cobertura.",