feat: add fluxer upstream source and self-hosting documentation

- Clone of github.com/fluxerapp/fluxer (official upstream)
- SELF_HOSTING.md: full VM rebuild procedure, architecture overview,
  service reference, step-by-step setup, troubleshooting, seattle reference
- dev/.env.example: all env vars with secrets redacted and generation instructions
- dev/livekit.yaml: LiveKit config template with placeholder keys
- fluxer-seattle/: existing seattle deployment setup scripts

fluxer/.github/workflows/restart-gateway.yaml

@@ -0,0 +1,78 @@
+name: restart gateway
+
+on:
+  workflow_dispatch:
+    inputs:
+      confirmation:
+        description: this will cause service interruption for all users. type RESTART to confirm.
+        required: true
+        type: string
+
+concurrency:
+  group: restart-gateway
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+env:
+  SERVICE_NAME: fluxer-gateway
+  IMAGE_NAME: fluxer-gateway
+  CONTEXT_DIR: fluxer_gateway
+  COMPOSE_STACK: fluxer-gateway
+  RELEASE_CHANNEL: ${{ github.ref_name == 'canary' && 'staging' || 'production' }}
+
+jobs:
+  restart:
+    name: Restart gateway
+    runs-on: blacksmith-8vcpu-ubuntu-2404
+    timeout-minutes: 25
+    steps:
+      - name: Validate confirmation
+        if: ${{ github.event.inputs.confirmation != 'RESTART' }}
+        run: python3 scripts/ci/workflows/restart_gateway.py --step validate_confirmation --confirmation "${{ github.event.inputs.confirmation }}"
+
+      - uses: actions/checkout@v6
+
+      - name: Record deploy commit
+        run: python3 scripts/ci/workflows/restart_gateway.py --step record_deploy_commit
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_PASSWORD }}
+
+      - name: Build image
+        uses: docker/build-push-action@v6
+        with:
+          context: ${{ env.CONTEXT_DIR }}
+          file: ${{ env.CONTEXT_DIR }}/Dockerfile
+          tags: ${{ env.IMAGE_NAME }}:${{ env.DEPLOY_SHA }}
+          load: true
+          platforms: linux/amd64
+          cache-from: type=gha,scope=${{ env.SERVICE_NAME }}
+          cache-to: type=gha,mode=max,scope=${{ env.SERVICE_NAME }}
+        env:
+          DOCKER_BUILD_SUMMARY: false
+          DOCKER_BUILD_RECORD_UPLOAD: false
+
+      - name: Install docker-pussh
+        run: python3 scripts/ci/workflows/restart_gateway.py --step install_docker_pussh
+
+      - name: Set up SSH agent
+        uses: webfactory/ssh-agent@v0.9.1
+        with:
+          ssh-private-key: ${{ secrets.SSH_PRIVATE_KEY_SERVER }}
+
+      - name: Add server to known hosts
+        run: python3 scripts/ci/workflows/restart_gateway.py --step add_known_hosts --server-ip ${{ secrets.SERVER_IP }}
+
+      - name: Push image and deploy
+        env:
+          IMAGE_TAG: ${{ env.IMAGE_NAME }}:${{ env.DEPLOY_SHA }}
+          SERVER: ${{ secrets.SERVER_USER }}@${{ secrets.SERVER_IP }}
+        run: python3 scripts/ci/workflows/restart_gateway.py --step push_and_deploy