Decouple translations artifact from the nightly build (#53602)

* Skip backend translations download in nightly build

The nightly only builds the app (build-app), which does not merge backend
translations — the shipped app fetches those from core at runtime. The
backend Lokalise export is a whole-project download across all languages
and the slowest part of the translations step. Skipping it, as the release
already does, cuts several minutes off every nightly.

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

* Decouple translations artifact into a parallel job

The full translations (including the slow Lokalise backend/core export) are
only needed for the uploaded `translations` artifact, not the wheel:
build-app does not merge backend translations. Move that download and the
artifact upload into a separate `translations` job that runs in parallel
with the build, so the backend export no longer sits on the build's
critical path. Both jobs run in the same workflow run, so consumers still
find both the `wheels` and `translations` artifacts.

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

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: bramkragten

.github/workflows/nightly.yaml

@@ -38,6 +38,11 @@ jobs:
         run: ./script/translations_download
         env:
           LOKALISE_TOKEN: ${{ secrets.LOKALISE_TOKEN }}
+          # The wheel only builds the app (build-app), which does not merge
+          # backend translations. Skipping the whole-project backend export (as
+          # the release does) keeps this off the build's critical path; the full
+          # translations artifact is produced in parallel by the job below.
+          SKIP_BACKEND_TRANSLATIONS: "1"
 
       - name: Bump version
         run: script/version_bump.js nightly
@@ -74,16 +79,38 @@ jobs:
           path: .compress-cache
           key: compress-cache-${{ runner.os }}-${{ github.run_id }}-${{ github.run_attempt }}
 
-      - name: Archive translations
-        run: tar -czvf translations.tar.gz translations
-
       - name: Upload build artifacts
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
           name: wheels
           path: dist/home_assistant_frontend*.whl
           if-no-files-found: error
 
+  # The full translations (including the slow backend/core export) are only
+  # needed for the uploaded artifact, not the wheel, so they are downloaded in
+  # parallel here instead of blocking the build above.
+  translations:
+    name: Translations
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+
+      - name: Setup Node and install
+        uses: ./.github/actions/setup
+        with:
+          immutable: false
+
+      - name: Download translations
+        run: ./script/translations_download
+        env:
+          LOKALISE_TOKEN: ${{ secrets.LOKALISE_TOKEN }}
+
+      - name: Archive translations
+        run: tar -czvf translations.tar.gz translations
+
       - name: Upload translations
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with: