chore: add workflow to auto-merge l10n PRs (#6948)

Co-authored-by: Michael Genson <71845777+michael-genson@users.noreply.github.com>

.github/workflows/auto-merge-l10n.yml

@@ -0,0 +1,89 @@
+name: Auto-merge l10n PRs
+
+on:
+  pull_request:
+    types: [opened, synchronize, labeled]
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  auto-merge:
+    runs-on: ubuntu-latest
+    if: contains(github.event.pull_request.labels.*.name, 'l10n')
+
+    steps:
+      - name: Generate GitHub App Token
+        id: app-token
+        uses: actions/create-github-app-token@v1
+        with:
+          app-id: ${{ secrets.COMMIT_BOT_APP_ID }}
+          private-key: ${{ secrets.COMMIT_BOT_APP_PRIVATE_KEY }}
+
+      - name: Validate PR author
+        env:
+          AUTHOR: ${{ github.event.pull_request.user.login }}
+        run: |
+          if [[ "$AUTHOR" != "hay-kot" && "$AUTHOR" != "github-actions[bot]" ]]; then
+            echo "::error::PR author must be hay-kot or github-actions[bot] for auto-merge (got: $AUTHOR)"
+            exit 1
+          fi
+          echo "Author validated: $AUTHOR"
+
+      - name: Validate PR size
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          REPO: ${{ github.repository }}
+        run: |
+          ADDITIONS=$(gh pr view "$PR_NUMBER" --repo "$REPO" --json additions --jq '.additions')
+          DELETIONS=$(gh pr view "$PR_NUMBER" --repo "$REPO" --json deletions --jq '.deletions')
+          TOTAL=$((ADDITIONS + DELETIONS))
+
+          echo "PR changes: +$ADDITIONS -$DELETIONS (total: $TOTAL lines)"
+
+          if [ "$TOTAL" -gt 200 ]; then
+            echo "::error::PR exceeds 200 line change limit ($TOTAL lines)"
+            exit 1
+          fi
+
+      - name: Validate file paths
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          REPO: ${{ github.repository }}
+        run: |
+          FILES=$(gh pr view "$PR_NUMBER" --repo "$REPO" --json files --jq '.files[].path')
+
+          for file in $FILES; do
+            if [[ ! "$file" =~ ^frontend/lang/ ]] && [[ ! "$file" =~ ^mealie/repos/seed/resources/[^/]+/locales/ ]]; then
+              echo "::error::Invalid file path: $file"
+              echo "Only files in frontend/lang/ or mealie/repos/seed/resources/*/locales/ are allowed"
+              exit 1
+            fi
+          done
+
+          echo "All files are in allowed paths"
+
+      - name: Approve PR
+        env:
+          GH_TOKEN: ${{ steps.app-token.outputs.token }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          REPO: ${{ github.repository }}
+        run: |
+          gh pr review "$PR_NUMBER" \
+            --repo "$REPO" \
+            --approve \
+            --body "Auto-approved: l10n PR from trusted author with valid file paths"
+
+      - name: Enable auto-merge
+        env:
+          GH_TOKEN: ${{ steps.app-token.outputs.token }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          REPO: ${{ github.repository }}
+        run: |
+          gh pr merge "$PR_NUMBER" \
+            --repo "$REPO" \
+            --auto \
+            --squash