Merge origin/main: Google Street View provider, translated

Main added the Google Street View street-level provider and key guidance
that offers another source. Its new text goes through t()/msg() with ru
and es entries; the key guidance the panel shows is built in the UI
language by src/ui/keyGuidance.js, while keySetupCore.mjs keeps the
English sentences the server and AI tools use.

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

src/ui/keyGuidance.js

@@ -0,0 +1,49 @@
+/**
+ * Key guidance in the UI language. keySetupCore.mjs builds the same sentences
+ * in English for the server and the AI tools; these are the ones people read.
+ */
+import {
+  KEY_SETUP_KEYS,
+  keySetupRequirementEnvVars,
+} from '../keySetupCore.mjs';
+import { t, translateKnown } from '../i18n/index.js';
+
+/** "Needs X — add it in Provider Settings", or '' for an unknown or hidden key. */
+export function keyRequirementText(id) {
+  const envVars = id ? keySetupRequirementEnvVars(id) : null;
+  return envVars
+    ? t('Needs {envVars} — add it in Provider Settings', { envVars })
+    : '';
+}
+
+/** The key's product name in title case: GOOGLE MAPS → Google Maps. */
+function keyName(id) {
+  const entry = KEY_SETUP_KEYS.find((candidate) => candidate.id === id);
+  return entry
+    ? entry.title
+        .toLowerCase()
+        .replace(/\b\w/g, (letter) => letter.toUpperCase())
+    : null;
+}
+
+/**
+ * The requirement, then the switched-off sources that would draw with a key
+ * already set (see keySetupWithAlternatives).
+ *
+ * @param {string} requirement
+ * @param {Array<{label: string, requiresKeyId: string|null}>} [alternatives]
+ */
+export function keyGuidanceText(requirement, alternatives = []) {
+  const options = alternatives.map(({ label, requiresKeyId }) => {
+    const name = keyName(requiresKeyId);
+    const source = translateKnown(label);
+    return name
+      ? t('light {source} to use your {name} key', { source, name })
+      : t('light {source}', { source });
+  });
+  if (!options.length) return requirement;
+  const offer = options.join(t(', or '));
+  if (requirement)
+    return t('{requirement}, or {offer}', { requirement, offer });
+  return offer.charAt(0).toLocaleUpperCase() + offer.slice(1);
+}