ci(i18n): translation parity guard + allow partial translations

Add scripts/check_translations.py and a lightweight Translations workflow
that runs it (no Android SDK needed) so Weblate PRs get fast feedback. The
script fails on stale keys (present in a translation but not the base) and on
translating translatable="false" entries; missing keys are reported as
coverage only.

Downgrade lint's MissingTranslation to informational: partial community
translations are expected and fall back to the English base at runtime.
Stale/extra keys (ExtraTranslation) remain fatal in lintDebug.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/translations.yaml

@@ -0,0 +1,41 @@
+name: Translations
+
+# Fast, SDK-free parity check for translation resources, so Weblate PRs (which
+# only touch values-*/strings.xml) get quick feedback without the full Android
+# build. The deeper checks still run in CI via lintDebug (ExtraTranslation).
+on:
+  push:
+    branches:
+      - '**'
+    tags-ignore:
+      - '**'
+    paths:
+      - 'app/src/main/res/values*/strings.xml'
+      - 'app/src/main/res/xml/locales_config.xml'
+      - 'scripts/check_translations.py'
+      - '.gitea/workflows/translations.yaml'
+
+concurrency:
+  group: translations-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    runs-on: docker
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Ensure python3
+        run: |
+          if ! command -v python3 >/dev/null 2>&1; then
+            if command -v apt-get >/dev/null 2>&1; then
+              apt-get update && apt-get install -y python3
+            elif command -v apk >/dev/null 2>&1; then
+              apk add --no-cache python3
+            fi
+          fi
+          python3 --version
+
+      - name: Check translation parity
+        run: python3 scripts/check_translations.py