feat(i18n): retire duplicate 'in' locale (alias to id) — 42 honest locales

`in` was a broken duplicate of `id`: config called it "Indonesian (Legacy)",
the README labelled it Hindi behind an Indian flag, and its dashboard catalog
was 45% English. Retiring it makes the supported-locale count an honest 42.

Saved preferences keep working: `id` now declares `"aliases": ["in"]`, so
`NEXT_LOCALE=in` (resolveRequestedLocale) and `OMNIROUTE_LANG=in`
(bin/cli/i18n.mjs detectLocale) both resolve to `id`.

Removed from every surface: config/i18n.json, the dashboard and CLI catalogs,
the docs mirror (docs/i18n/in/), the README flag block and headline, the
docs indexes, llm.txt (+ the 41 llm.txt mirrors), the i18n-flow diagram,
the Google-Translate generator specs, the CLI scaffold list, the Python
lang map, the translation-ratio baseline and .i18n-state.json.

The 🌐 language bars of the seven English docs that linked ../i18n/in/ lost
that entry too, otherwise check:doc-links would resolve to a deleted tree.

bin/cli/scripts/generate-locales.mjs

@@ -890,7 +890,7 @@ const TRANSLATIONS = {
 
 // Languages with no translation in this script — will be created as empty objects
 // All keys fall back to `en` via i18n.mjs's fallback mechanism.
-const SCAFFOLD_ONLY = ["bn", "gu", "he", "in", "mr", "ms", "phi", "sw", "ta", "te", "ur"];
+const SCAFFOLD_ONLY = ["bn", "gu", "he", "mr", "ms", "phi", "sw", "ta", "te", "ur"];
 
 let created = 0;
 let skipped = 0;