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.

src/sources/live/standalone.js

@@ -66,6 +66,7 @@ export function createFlightSource({
   now = () => Date.now(),
 } = {}) {
   return {
+    // i18n-ignore: feed source name, replaced by the provider from each snapshot and reported to AI tools
     label: 'Flights',
     async getSnapshot(query = {}, { signal } = {}) {
       const params = new URLSearchParams();
@@ -127,6 +128,7 @@ export function createMilitarySource({
   now = () => Date.now(),
 } = {}) {
   return {
+    // i18n-ignore: feed source name, replaced by the provider from each snapshot and reported to AI tools
     label: 'Military aircraft',
     async getIdentities(_query = {}, { signal } = {}) {
       const { response, payload } = await readResponse(
@@ -186,6 +188,7 @@ export function createVesselSource({
   origin = () => globalThis.location?.origin || 'http://localhost',
 } = {}) {
   return {
+    // i18n-ignore: feed source name, replaced by the provider from each snapshot and reported to AI tools
     label: 'Vessels',
     async getSnapshot({ maxRows = 12000, area } = {}, { signal } = {}) {
       const url = new URL(apiUrl, origin());