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/fluxer_admin/Dockerfile

@@ -0,0 +1,85 @@
+ARG BUILD_SHA
+ARG BUILD_NUMBER
+ARG BUILD_TIMESTAMP
+ARG RELEASE_CHANNEL=nightly
+
+FROM node:24-bookworm-slim AS base
+
+WORKDIR /usr/src/app
+
+RUN corepack enable && corepack prepare pnpm@10.26.0 --activate
+
+FROM base AS deps
+
+COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
+COPY patches/ ./patches/
+COPY packages/ ./packages/
+COPY fluxer_admin/package.json ./fluxer_admin/
+
+RUN pnpm install --frozen-lockfile
+
+FROM deps AS build
+
+COPY tsconfigs /usr/src/app/tsconfigs
+COPY fluxer_admin/tsconfig.json ./fluxer_admin/
+COPY fluxer_admin/src ./fluxer_admin/src
+COPY fluxer_admin/public ./fluxer_admin/public
+
+WORKDIR /usr/src/app/fluxer_admin
+RUN pnpm --filter @fluxer/config generate
+RUN pnpm build:css
+
+FROM base AS prod-deps
+
+COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
+COPY patches/ ./patches/
+COPY packages/ ./packages/
+COPY fluxer_admin/package.json ./fluxer_admin/
+
+RUN pnpm install --frozen-lockfile --prod
+
+COPY --from=build /usr/src/app/packages/admin/public /usr/src/app/packages/admin/public
+
+FROM node:24-bookworm-slim
+
+ARG BUILD_SHA
+ARG BUILD_NUMBER
+ARG BUILD_TIMESTAMP
+ARG RELEASE_CHANNEL
+
+WORKDIR /usr/src/app/fluxer_admin
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+	curl && \
+	rm -rf /var/lib/apt/lists/*
+
+RUN corepack enable && corepack prepare pnpm@10.26.0 --activate
+
+COPY --from=prod-deps /usr/src/app/node_modules /usr/src/app/node_modules
+COPY --from=prod-deps /usr/src/app/fluxer_admin/node_modules ./node_modules
+COPY --from=prod-deps /usr/src/app/packages /usr/src/app/packages
+COPY --from=build /usr/src/app/packages/config/src/ConfigSchema.json /usr/src/app/packages/config/src/ConfigSchema.json
+COPY --from=build /usr/src/app/packages/config/src/MasterZodSchema.generated.tsx /usr/src/app/packages/config/src/MasterZodSchema.generated.tsx
+COPY tsconfigs /usr/src/app/tsconfigs
+COPY --from=build /usr/src/app/fluxer_admin/tsconfig.json ./tsconfig.json
+COPY --from=build /usr/src/app/fluxer_admin/src ./src
+COPY --from=build /usr/src/app/fluxer_admin/public ./public
+COPY fluxer_admin/package.json ./
+
+RUN mkdir -p /usr/src/app/.cache/corepack && \
+	chown -R nobody:nogroup /usr/src/app
+
+ENV HOME=/usr/src/app
+ENV COREPACK_HOME=/usr/src/app/.cache/corepack
+ENV NODE_ENV=production
+ENV FLUXER_ADMIN_PORT=8080
+ENV BUILD_SHA=${BUILD_SHA}
+ENV BUILD_NUMBER=${BUILD_NUMBER}
+ENV BUILD_TIMESTAMP=${BUILD_TIMESTAMP}
+ENV RELEASE_CHANNEL=${RELEASE_CHANNEL}
+
+USER nobody
+
+EXPOSE 8080
+
+CMD ["pnpm", "start"]