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/deploy-admin.yaml

@@ -0,0 +1,112 @@
+name: deploy admin
+
+on:
+  push:
+    branches:
+      - main
+      - canary
+    paths:
+      - fluxer_admin/**
+      - .github/workflows/deploy-admin.yaml
+  workflow_dispatch:
+    inputs:
+      channel:
+        type: choice
+        options:
+          - stable
+          - canary
+        default: stable
+        description: Release channel to deploy
+      ref:
+        type: string
+        required: false
+        default: ''
+        description: Optional git ref (defaults to the triggering branch)
+
+concurrency:
+  group: deploy-fluxer-admin-${{ github.event_name == 'workflow_dispatch' && inputs.channel || (github.ref_name == 'canary' && 'canary') || 'stable' }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+jobs:
+  channel-vars:
+    uses: ./.github/workflows/channel-vars.yaml
+    with:
+      github_event_name: ${{ github.event_name }}
+      github_ref_name: ${{ github.ref_name }}
+      workflow_dispatch_channel: ${{ github.event_name == 'workflow_dispatch' && inputs.channel || '' }}
+
+  deploy:
+    name: Deploy admin
+    needs: channel-vars
+    runs-on: blacksmith-8vcpu-ubuntu-2404
+    timeout-minutes: 25
+    env:
+      CHANNEL: ${{ needs.channel-vars.outputs.channel }}
+      IS_CANARY: ${{ needs.channel-vars.outputs.is_canary }}
+      STACK_SUFFIX: ${{ needs.channel-vars.outputs.stack_suffix }}
+      STACK: ${{ format('fluxer-admin{0}', needs.channel-vars.outputs.stack_suffix) }}
+      CACHE_SCOPE: ${{ format('deploy-fluxer-admin{0}', needs.channel-vars.outputs.stack_suffix) }}
+      CADDY_DOMAIN: ${{ needs.channel-vars.outputs.is_canary == 'true' && 'admin.canary.fluxer.app' || 'admin.fluxer.app' }}
+      REPLICAS: ${{ needs.channel-vars.outputs.is_canary == 'true' && 1 || 2 }}
+      RELEASE_CHANNEL: ${{ needs.channel-vars.outputs.channel }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          ref: ${{ inputs.ref || '' }}
+          fetch-depth: 0
+
+      - name: Record deploy commit
+        run: python3 scripts/ci/workflows/deploy_admin.py --step record_deploy_commit
+
+      - name: Set build timestamp
+        run: python3 scripts/ci/workflows/deploy_admin.py --step set_build_timestamp
+
+      - 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: .
+          file: fluxer_admin/Dockerfile
+          tags: ${{ env.STACK }}:${{ env.DEPLOY_SHA }}
+          load: true
+          platforms: linux/amd64
+          cache-from: type=gha,scope=${{ env.CACHE_SCOPE }}
+          cache-to: type=gha,mode=max,scope=${{ env.CACHE_SCOPE }}
+          build-args: |
+            BUILD_SHA=${{ env.DEPLOY_SHA }}
+            BUILD_NUMBER=${{ github.run_number }}
+            BUILD_TIMESTAMP=${{ env.BUILD_TIMESTAMP }}
+            RELEASE_CHANNEL=${{ env.RELEASE_CHANNEL }}
+        env:
+          DOCKER_BUILD_SUMMARY: false
+          DOCKER_BUILD_RECORD_UPLOAD: false
+
+      - name: Install docker-pussh
+        run: python3 scripts/ci/workflows/deploy_admin.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/deploy_admin.py --step add_known_hosts --server-ip ${{ secrets.SERVER_IP }}
+
+      - name: Push image and deploy
+        env:
+          IMAGE_TAG: ${{ env.STACK }}:${{ env.DEPLOY_SHA }}
+          SERVER: ${{ secrets.SERVER_USER }}@${{ secrets.SERVER_IP }}
+          STACK: ${{ env.STACK }}
+          CADDY_DOMAIN: ${{ env.CADDY_DOMAIN }}
+          REPLICAS: ${{ env.REPLICAS }}
+        run: python3 scripts/ci/workflows/deploy_admin.py --step push_and_deploy