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>

.github/workflows/release.yml

@@ -35,6 +35,11 @@ jobs:
         id: meta
         run: echo "version=${GITHUB_REF_NAME#v}" >> "$GITHUB_OUTPUT"
 
+      # QEMU lets the amd64 runner emulate arm64 so the images below build for
+      # both platforms (Intel + Apple Silicon self-hosters).
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
       - name: Set up Buildx
         uses: docker/setup-buildx-action@v3
 
@@ -49,6 +54,7 @@ jobs:
         with:
           context: ./backend
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: |
             ${{ env.REGISTRY_NAMESPACE }}/temetro-backend:${{ steps.meta.outputs.version }}
             ${{ env.REGISTRY_NAMESPACE }}/temetro-backend:latest
@@ -58,6 +64,7 @@ jobs:
         with:
           context: ./frontend
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: |
             ${{ env.REGISTRY_NAMESPACE }}/temetro-frontend:${{ steps.meta.outputs.version }}
             ${{ env.REGISTRY_NAMESPACE }}/temetro-frontend:latest