refactor(i18n): key messages by English text; add Russian

Replace the semantic keys with the English source text, so code reads as the
UI does and English needs no catalog: t('Save keys'), tn(count, one, other)
for plurals, msg() for text stored in data, and bare data-i18n* markup that
translates the element's own English. Other languages are one flat JSON each.

- Simplify src/i18n: drop namespaces, the configurable locale pair
  (GEV_DEFAULT_LOCALE / GEV_SECONDARY_LOCALE) and its build defines. Locale
  comes from ?lang=, the stored choice, then browser languages.
- Add scripts/i18n.mjs (npm run i18n): extracts every message from t/tn/msg
  and markup, and fails on missing, unused, placeholder-mismatched or
  wrongly-shaped plural entries. npm test runs it via catalog.test.mjs.
- Add Russian (src/i18n/locales/ru.json, 833 messages), started from the
  community catalog in #312 and reviewed against the current English.
- Fix data-i18n placed on parents that would wipe their children (cockpit
  LEVEL and local weather cells, first-run EXPLORE MANUALLY tile), and a
  doubled degree sign in the TRACK ACQUIRED signal.
- Rewrite docs/TRANSLATORS.md for the new workflow; drop sections the earlier
  merge resurrected in docs/CURRENT-STATE.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/keySetupCore.mjs

@@ -32,11 +32,15 @@ export const KEY_SETUP_APPEND_HEADER =
  * bundle by design (restrict them at the provider, per SECURITY.md).
  * `hidden` keeps advanced configuration out of the panel and missing-key count.
  */
+// Marks `unlocks` copy for i18n extraction; Provider Settings translates it
+// with t(). Kept local so the server can import this module without i18n.
+const msg = (text) => text;
+
 export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'google-maps',
     title: 'GOOGLE MAPS',
-    unlocks: 'The photorealistic 3D planet + place search',
+    unlocks: msg('The photorealistic 3D planet + place search'),
     getUrl: 'https://developers.google.com/maps/documentation/tile/get-api-key',
     envVars: Object.freeze(['GOOGLE_MAPS_API_KEY']),
     tier: 'metered',
@@ -45,7 +49,9 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'google-maps-server',
     title: 'GOOGLE MAPS — SERVER',
-    unlocks: 'Places context + Street View fallback; optional separate key',
+    unlocks: msg(
+      'Places context + Street View fallback; optional separate key',
+    ),
     getUrl:
       'https://developers.google.com/maps/documentation/places/web-service/get-api-key',
     envVars: Object.freeze(['GOOGLE_MAPS_SERVER_API_KEY']),
@@ -55,7 +61,7 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'openai',
     title: 'OPENAI',
-    unlocks: 'Voice control — API key or ChatGPT OAuth',
+    unlocks: msg('Voice control — API key or ChatGPT OAuth'),
     getUrl: 'https://platform.openai.com/api-keys',
     envVars: Object.freeze(['OPENAI_API_KEY']),
     tier: 'metered',
@@ -63,7 +69,7 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'aisstream',
     title: 'AISSTREAM',
-    unlocks: 'Live ships, worldwide',
+    unlocks: msg('Live ships, worldwide'),
     getUrl: 'https://aisstream.io',
     envVars: Object.freeze(['AISSTREAM_API_KEY']),
     tier: 'free',
@@ -71,7 +77,7 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'firms',
     title: 'NASA FIRMS',
-    unlocks: 'Live active-fire detections',
+    unlocks: msg('Live active-fire detections'),
     getUrl: 'https://firms.modaps.eosdis.nasa.gov/api/map_key/',
     envVars: Object.freeze(['FIRMS_MAP_KEY']),
     tier: 'free',
@@ -79,7 +85,7 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'tomtom',
     title: 'TOMTOM',
-    unlocks: 'Real live traffic (keyless runs a simulation)',
+    unlocks: msg('Real live traffic (keyless runs a simulation)'),
     getUrl: 'https://my.tomtom.com/keys',
     envVars: Object.freeze(['TOMTOM_API_KEY']),
     tier: 'free',
@@ -87,7 +93,7 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'cesium-ion',
     title: 'CESIUM ION',
-    unlocks: 'Bing imagery map stacks + world terrain',
+    unlocks: msg('Bing imagery map stacks + world terrain'),
     getUrl: 'https://ion.cesium.com/tokens',
     envVars: Object.freeze(['CESIUM_ION_TOKEN']),
     tier: 'free',
@@ -96,7 +102,7 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'opensky',
     title: 'OPENSKY',
-    unlocks: 'More flight-polling credits (anonymous works without)',
+    unlocks: msg('More flight-polling credits (anonymous works without)'),
     getUrl: 'https://opensky-network.org',
     envVars: Object.freeze(['OPENSKY_CLIENT_ID', 'OPENSKY_CLIENT_SECRET']),
     tier: 'free',
@@ -104,8 +110,9 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'mapillary',
     title: 'MAPILLARY',
-    unlocks:
+    unlocks: msg(
       'Street-level imagery and coverage in the Street Level layer. Free: register an app in the Mapillary developer dashboard and paste its Client Token',
+    ),
     getUrl: 'https://www.mapillary.com/dashboard/developers',
     envVars: Object.freeze(['MAPILLARY_CLIENT_TOKEN']),
     tier: 'free',
@@ -114,7 +121,7 @@ export const KEY_SETUP_KEYS = Object.freeze([
   Object.freeze({
     id: 'launch-library',
     title: 'LAUNCH LIBRARY',
-    unlocks: 'Higher space-missions request allowance',
+    unlocks: msg('Higher space-missions request allowance'),
     getUrl: 'https://thespacedevs.com',
     envVars: Object.freeze(['LL2_API_TOKEN']),
     tier: 'free',