Add Dockerfile-based Dokku deployment for monorepo layout

Uses a multi-stage Docker build that copies both app/ and blogex/,
preserving the path dependency. Includes release scripts, migration
module, and a sample Dokku setup script.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.dockerignore

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+# Git
+.git
+
+# Build artifacts
+app/_build
+app/deps
+blogex/_build
+blogex/deps
+
+# Dev/test only
+app/test
+blogex/test
+app/.formatter.exs
+blogex/.formatter.exs
+
+# IDE
+.devcontainer
+.claude
+
+# Documentation
+*.md
+!app/README.md
+
+# Misc
+app/tmp
+app/cover
+app/doc
+blogex/doc
+
+# Dokku setup (may contain secrets)
+dokku-setup.sh

.gitignore

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+# Dokku setup (may contain secrets)
+dokku-setup.sh

Dockerfile

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+# Dockerfile for Dokku deployment
+# Multi-stage build for Phoenix/Elixir app with monorepo layout
+
+ARG ELIXIR_VERSION=1.18.3
+ARG OTP_VERSION=27.2.4
+ARG DEBIAN_VERSION=bookworm-20260316-slim
+
+ARG BUILDER_IMAGE="docker.io/hexpm/elixir:${ELIXIR_VERSION}-erlang-${OTP_VERSION}-debian-${DEBIAN_VERSION}"
+ARG RUNNER_IMAGE="docker.io/debian:${DEBIAN_VERSION}"
+
+# =============================================================================
+# Build stage
+# =============================================================================
+FROM ${BUILDER_IMAGE} AS builder
+
+RUN apt-get update -y && apt-get install -y build-essential git \
+    && apt-get clean && rm -f /var/lib/apt/lists/*_*
+
+WORKDIR /build
+
+# Install hex + rebar
+RUN mix local.hex --force && \
+    mix local.rebar --force
+
+ENV MIX_ENV="prod"
+
+# Copy blogex dependency first (changes less often)
+COPY blogex /build/blogex
+
+# Copy app dependency files first for better layer caching
+COPY app/mix.exs app/mix.lock /build/app/
+WORKDIR /build/app
+
+RUN mix deps.get --only $MIX_ENV
+RUN mkdir config
+
+# Copy compile-time config files
+COPY app/config/config.exs app/config/${MIX_ENV}.exs config/
+RUN mix deps.compile
+
+# Copy application source and compile
+COPY app/priv priv
+COPY app/assets assets
+COPY app/lib lib
+COPY app/rel rel
+COPY app/config/runtime.exs config/
+
+RUN mix compile
+
+# Build assets after compile (phoenix-colocated hooks need compiled app)
+RUN mix assets.deploy
+
+# Build the release
+RUN mix release
+
+# =============================================================================
+# Runtime stage
+# =============================================================================
+FROM ${RUNNER_IMAGE}
+
+RUN apt-get update -y && \
+    apt-get install -y libstdc++6 openssl libncurses5 locales ca-certificates \
+    && apt-get clean && rm -f /var/lib/apt/lists/*_*
+
+# Set the locale
+RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
+
+WORKDIR /app
+
+RUN chown nobody /app
+ENV MIX_ENV="prod"
+
+# Copy the release from the build stage
+COPY --from=builder --chown=nobody:root /build/app/_build/${MIX_ENV}/rel/firehose ./
+
+USER nobody
+
+# Dokku uses the EXPOSE port for routing
+EXPOSE 4000
+
+ENV PHX_SERVER=true
+
+CMD ["/app/bin/server"]

app.json

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+{
+  "name": "firehose",
+  "scripts": {
+    "dokku": {
+      "postdeploy": "/app/bin/migrate"
+    }
+  }
+}

app/lib/firehose/release.ex

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+defmodule Firehose.Release do
+  @moduledoc """
+  Tasks for production releases (e.g., database migrations).
+
+  Usage from Dokku:
+      dokku run APP_NAME /app/bin/migrate
+  """
+
+  @app :firehose
+
+  def migrate do
+    load_app()
+
+    for repo <- repos() do
+      {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :up, all: true))
+    end
+  end
+
+  def rollback(repo, version) do
+    load_app()
+    {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :down, to: version))
+  end
+
+  defp repos do
+    Application.fetch_env!(@app, :ecto_repos)
+  end
+
+  defp load_app do
+    Application.load(@app)
+  end
+end

app/rel/overlays/bin/migrate

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+#!/bin/sh
+set -eu
+
+cd -P -- "$(dirname -- "$0")"/..
+
+exec ./bin/firehose eval Firehose.Release.migrate

app/rel/overlays/bin/server

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+#!/bin/sh
+set -eu
+
+cd -P -- "$(dirname -- "$0")"/..
+
+PHX_SERVER=true exec ./bin/firehose start

dokku-setup.sh.sample

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+#!/bin/bash
+# dokku-setup.sh.sample - Set up Dokku app for firehose
+#
+# USAGE:
+#   1. Copy to dokku-setup.sh: cp dokku-setup.sh.sample dokku-setup.sh
+#   2. Fill in any empty strings below
+#   3. Run on Dokku server: ./dokku-setup.sh
+#
+# Do NOT commit dokku-setup.sh (contains secrets)
+
+set -e
+
+APP="firehose"        # <-- change to your desired Dokku app name / hostname
+PHX_HOST="$APP"       # <-- change to your full domain, e.g., firehose.example.com
+
+# Auto-generate secrets
+SECRET_KEY_BASE=$(openssl rand -base64 64 | tr -d '\n')
+
+echo "==> Creating Dokku app: $APP"
+dokku apps:create "$APP" || echo "App may already exist"
+
+echo "==> Creating PostgreSQL database"
+dokku postgres:create "${APP}-db" || echo "Database may already exist"
+dokku postgres:link "${APP}-db" "$APP" || echo "Database may already be linked"
+
+echo "==> Setting environment variables"
+dokku config:set --no-restart "$APP" \
+  SECRET_KEY_BASE="$SECRET_KEY_BASE" \
+  PHX_HOST="$PHX_HOST" \
+  PORT="4000"
+
+# Optional: set custom domain (uncomment and edit)
+# dokku domains:set "$APP" "$PHX_HOST"
+
+# Optional: set up SSL with Let's Encrypt (uncomment)
+# dokku letsencrypt:enable "$APP"
+
+echo ""
+echo "==> Setup complete!"
+echo ""
+echo "Next steps:"
+echo "  1. From your local machine, add the git remote:"
+echo "     git remote add dokku dokku@YOUR_SERVER:$APP"
+echo ""
+echo "  2. Push to deploy:"
+echo "     git push dokku main"
+echo ""
+echo "  3. Run migrations (first deploy):"
+echo "     dokku run $APP /app/bin/migrate"