add staging github actions

.github/workflows/fly-deploy-staging.yml

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+
+name: Fly Deploy (staging)
+
+on:
+  workflow_run:
+    workflows: ["Publish to ghcr (staging)"]
+    types:
+      - completed
+
+jobs:
+  deploy:
+    name: Deploy staging app
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          submodules: 'true'
+
+      - name: Use flyctl
+        uses: superfly/flyctl-actions/setup-flyctl@master
+
+      - name: Deploy to fly.io
+        run: flyctl deploy --local-only
+        env:
+          FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}
+        working-directory: ./staging

.github/workflows/staging-ghcr-public.yml

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+
+name: Publish to ghcr (staging)
+
+on:
+  push:
+    branches: ["v3"]
+
+env:
+  REGISTRY_IMAGE: ghcr.io/sourcebot-dev/sourcebot
+
+jobs:
+  build:
+    runs-on: ${{ matrix.runs-on}}
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+    strategy:
+      matrix:
+        platform: [linux/amd64, linux/arm64]
+        include:
+          - platform: linux/amd64
+            runs-on: ubuntu-latest
+          - platform: linux/arm64
+            runs-on: ubuntu-24.04-arm
+
+    steps:
+      - name: Prepare
+        run: |
+          platform=${{ matrix.platform }}
+          echo "PLATFORM_PAIR=${platform//\//-}" >> $GITHUB_ENV
+
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          submodules: "true"
+
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY_IMAGE }}
+          tags: staging
+
+      - name: Install cosign
+        uses: sigstore/cosign-installer@v3.5.0
+        with:
+          cosign-release: "v2.2.4"
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to GitHub Packages Docker Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build Docker image
+        id: build
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          platforms: ${{ matrix.platform }}
+          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true,push=true
+          build-args: |
+            SOURCEBOT_VERSION=${{ github.ref_name }}
+            POSTHOG_PAPIK=${{ secrets.POSTHOG_PAPIK }}
+            SOURCEBOT_ENCRYPTION_KEY=${{ secrets.STAGING_SOURCEBOT_ENCRYPTION_KEY }}
+
+      - name: Export digest
+        run: |
+          mkdir -p /tmp/digests
+          digest="${{ steps.build.outputs.digest }}"
+          touch "/tmp/digests/${digest#sha256:}"
+
+      - name: Upload digest
+        uses: actions/upload-artifact@v4
+        with:
+          name: digests-${{ env.PLATFORM_PAIR }}
+          path: /tmp/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+      - name: Sign the published Docker image
+        env:
+          TAGS: ${{ steps.meta.outputs.tags }}
+          DIGEST: ${{ steps.build.outputs.digest }}
+        run: echo "${TAGS}" | xargs -I {} cosign sign --yes {}@${DIGEST}
+  
+  merge:
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+    needs:
+      - build
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: /tmp/digests
+          pattern: digests-*
+          merge-multiple: true
+      
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY_IMAGE }}
+          tags: staging
+
+      - name: Login to GitHub Packages Docker Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      
+      - name: Create manifest list and push
+        working-directory: /tmp/digests
+        run: |
+          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf '${{ env.REGISTRY_IMAGE }}@sha256:%s ' *)
+      
+      - name: Inspect image
+        run: |
+          docker buildx imagetools inspect ${{ env.REGISTRY_IMAGE }}:${{ steps.meta.outputs.version }}