Add Docker build and compose setup

Three-stage build: bun compiles the frontend, cargo embeds it into the
release binary, and the runtime stage carries only that binary on
debian:trixie-slim as an unprivileged user.

compose.yml pins DIARY_BIND and DIARY_DATA_DIR over whatever .env says,
keeps state in a named volume, publishes on localhost only and probes the
port with bash so the image needs no curl. compose.override.yml.example
shows the traefik overlay for the personal host.

.dockerignore

@@ -0,0 +1,11 @@
+.git
+.env
+target
+data
+web/dist
+web/node_modules
+README.md
+Makefile
+Dockerfile
+.dockerignore
+compose*.yml

.gitignore

@@ -10,3 +10,6 @@
 
 # secrets
 .env
+
+# host-specific compose overlay
+compose.override.yml

Dockerfile

@@ -0,0 +1,36 @@
+# syntax=docker/dockerfile:1
+
+# 1. Frontend. Built first so a Rust-only change does not re-run bun.
+FROM oven/bun:1-alpine AS web
+WORKDIR /web
+COPY web/package.json web/bun.lock ./
+RUN bun install --frozen-lockfile
+COPY web/ ./
+RUN bun run build
+
+# 2. Backend. rust-embed bakes web/dist into the binary in release mode,
+#    so the result is a single self-contained executable.
+FROM rust:1-slim-trixie AS build
+WORKDIR /app
+COPY Cargo.toml Cargo.lock ./
+COPY src/ ./src/
+COPY migrations/ ./migrations/
+COPY --from=web /web/dist/ ./web/dist/
+RUN --mount=type=cache,target=/usr/local/cargo/registry \
+    --mount=type=cache,target=/app/target \
+    cargo build --release --locked \
+ && cp target/release/narl-diary /usr/local/bin/narl-diary
+
+# 3. Runtime. SQLite is compiled into the binary, so nothing else is needed.
+FROM debian:trixie-slim
+RUN useradd --system --uid 10001 --create-home --home-dir /home/diary diary \
+ && mkdir -p /data \
+ && chown diary:diary /data
+COPY --from=build /usr/local/bin/narl-diary /usr/local/bin/narl-diary
+USER diary
+WORKDIR /home/diary
+VOLUME ["/data"]
+ENV DIARY_BIND=0.0.0.0:4242 \
+    DIARY_DATA_DIR=/data
+EXPOSE 4242
+ENTRYPOINT ["/usr/local/bin/narl-diary"]

README.md

@@ -92,3 +92,22 @@ Everything except the two share routes requires the session cookie.
 Put a TLS-terminating reverse proxy in front of it, point it at `DIARY_BIND`,
 and set `DIARY_SECURE_COOKIE=1`. Nothing else is needed: no database server, no
 runtime dependencies, no build tools on the host.
+
+### Docker
+
+```sh
+cp .env.example .env   # set DIARY_USER, DIARY_PASSWORD, DIARY_SECRET
+docker compose up -d --build
+```
+
+The image builds the frontend with bun and the binary with cargo, then ships
+only the binary on `debian:trixie-slim` (~86 MB), running as an unprivileged
+user. `DIARY_BIND` and `DIARY_DATA_DIR` are forced in `compose.yml`, so the
+values in `.env` do not have to change; everything else is read from `.env`.
+Database and uploads live in the `diary-data` volume and survive recreation.
+
+By default the port is published on `127.0.0.1:4242` only. To serve it through
+traefik instead, copy `compose.override.yml.example` to `compose.override.yml`
+and adjust the host — it joins the external `narl` network, drops the published
+port, and routes to container port 4242. Set `DIARY_SECURE_COOKIE=1` in `.env`
+once it is served over HTTPS.

compose.override.yml.example

@@ -0,0 +1,18 @@
+# Copy to compose.override.yml on the host that runs traefik.
+services:
+  diary:
+    ports: !override []
+    networks:
+      - narl
+      - internal_net
+    labels:
+      - "traefik.enable=true"
+      - "traefik.docker.network=narl"
+      - "traefik.http.routers.diary.rule=Host(`diary.narl.io`)"
+      - "traefik.http.routers.diary.entrypoints=websecure"
+      - "traefik.http.routers.diary.tls.certresolver=https_resolver"
+      - "traefik.http.services.diary.loadbalancer.server.port=4242"
+
+networks:
+  narl:
+    external: true

compose.yml

@@ -0,0 +1,33 @@
+services:
+  diary:
+    build: .
+    image: narl-diary:latest
+    restart: unless-stopped
+    env_file:
+      - .env
+    environment:
+      # These win over anything in .env: inside the container the app must
+      # listen on all interfaces and keep its state on the volume.
+      DIARY_BIND: 0.0.0.0:4242
+      DIARY_DATA_DIR: /data
+    volumes:
+      - diary-data:/data
+    networks:
+      - internal_net
+    ports:
+      # Localhost only. Drop this in the override when a reverse proxy
+      # reaches the container over its own network instead.
+      - "127.0.0.1:4242:4242"
+    healthcheck:
+      # No extra tooling in the image, so probe the port with bash directly.
+      test: ["CMD", "bash", "-c", "exec 3<>/dev/tcp/127.0.0.1/4242"]
+      interval: 30s
+      timeout: 3s
+      start_period: 5s
+      retries: 3
+
+volumes:
+  diary-data:
+
+networks:
+  internal_net: