release workflow: publish multi-arch images; settings: confirm language switch

- release.yml: add QEMU + platforms: linux/amd64,linux/arm64 to both
  build-push steps so the published images work on Apple Silicon (fixes
  'no matching manifest for linux/arm64/v8' on docker compose pull).
- Settings -> Profile language picker is now a select that opens a
  confirmation dialog before applying, instead of switching instantly.
- CLAUDE.md: require a dated docs changelog entry for every release.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -80,6 +80,11 @@ accurate (e.g. a new backend route needs an `content/docs/api/*.mdx` entry; a UI
 in the matching guide; status changes belong in the roadmap). Commit docs changes inside that
 repo, separately from this one.
 
+**Every release must also get a dated entry in the docs changelog**
+(`content/docs/changelog.mdx`, newest first) — not just the monorepo `CHANGELOG.md`. When you cut a
+version (see "Always release after pushing"), add a matching, user-facing section to that page in the
+same session so `../temetro/docs` never falls behind the shipped version.
+
 ## Running the stack
 
 From `backend/`: ensure a `.env` exists (`cp .env.example .env`, then set `BETTER_AUTH_SECRET` via