Add Deployment section to README

Document production deployment including:
- Multi-stage Docker image build process (build + production stages)
- Docker Compose setup with env substitution and restart policy
- Required production environment variables with notes
- Persistent SQLite data volume management, backup and migration

README.md

@@ -176,3 +176,108 @@ pnpm test:unit       # Run unit tests (vitest)
 pnpm test            # Run integration tests (bash E2E)
 pnpm test:server     # Start server for manual testing
 ```
+
+## Deployment
+
+### Production Image Build
+
+Mailship uses a **multi-stage Docker build** to produce a minimal production image.
+
+| Stage | Base Image | Purpose |
+|---|---|---|
+| `build` | `node:22-alpine` | Compile TypeScript, install all dependencies |
+| `production` | `node:22-alpine` | Runtime — only production deps, compiled JS, static assets |
+
+The Dockerfile is structured to keep the final image small by discarding build tooling
+(`python3`, `make`, `g++`, `git`) and development dependencies after compilation.
+
+```sh
+docker build -t mailship .
+```
+
+The image listens on **port 4738**, expects a writable **`/data`** volume for the SQLite
+database, and runs as a non-root user (`app`) for security hardening.
+
+### Docker Compose (Recommended)
+
+Copy the environment template, fill in your secrets, and start:
+
+```sh
+cp .env.template .env
+# Edit .env with your production values (see Required Environment Variables below)
+docker compose up -d
+```
+
+The compose file (`docker-compose.yml`) configures:
+
+- **Automatic restarts** via `restart: unless-stopped`
+- **Named volume** `mailship-data` mounted at `/data` for database persistence
+- **Port 4738** published to the host
+- **Environment variables** passed from your `.env` file with `.env` substitution
+- **Required vars** (`MAILSHIP_SECRET`, `MAILSHIP_URL`, `BASE_URL`, `SMTP_*`) — the
+  compose file uses `${VAR:?required}` to fail early if any are missing
+
+To pull the latest image and recreate the container after a rebuild:
+
+```sh
+docker compose build --pull
+# or if using a pre-built image:
+docker compose pull
+docker compose up -d
+```
+
+### Required Environment Variables
+
+The table below marks variables that are especially important in **production**.
+Defaults are safe for development but may leak information or misroute mail in a
+production deployment.
+
+| Variable | Required in production | Notes |
+|---|---|---|
+| `MAILSHIP_SECRET` | ✓ | Must be a **private key in hex** — never share or commit this value |
+| `MAILSHIP_URL` | ✓ | Set to the **public-facing URL** of your instance (e.g. `https://mail.example.com`) |
+| `BASE_URL` | ✓ | Same as `MAILSHIP_URL` in most setups; used for callback URLs in email |
+| `SMTP_HOST` | ✓ | Production SMTP server (e.g. `smtp.sendgrid.net`, `email-smtp.us-east-1.amazonaws.com`) |
+| `SMTP_PORT` | ✓ | 587 (STARTTLS) or 465 (TLS); verify with your provider |
+| `SMTP_USER` | ✓ | SMTP authentication username |
+| `SMTP_PASSWORD` | ✓ | SMTP authentication password — use a secret manager or env injection, not a file |
+| `SMTP_FROM` | ✓ | The `From:` address recipients will see (e.g. `"Mailship" <notifications@example.com>`) |
+| `DEFAULT_RELAYS` | | Comma-separated relay list; production should tune these to reliable relays |
+| `INDEXER_RELAYS` | | Same — use relays you trust for discovery |
+| `SEARCH_RELAYS` | | Same — use a relay that supports NIP-50 search |
+| `CORS_ORIGIN` | ✓ | **Must** be set to the exact origin your browser client runs on (e.g. `https://app.example.com`). The server refuses to start without it. |
+| `DATA_DIR` | | Default `/data` in the Docker image; change only if you mount a different volume path |
+| `BRAND_NAME`, `BRAND_ACCENT`, `BRAND_LOGO` | | Branding overrides — safe to leave at defaults |
+| `EVENT_VIEWER_URL` | | Controls where event links in emails point; defaults to Flotilla, set to your app's URL |
+| `PORT` | | Internal port (default `4738`) — no need to change unless remapping in compose |
+
+> **Secrets in production:** Never commit `.env` or embed secrets in the compose
+> file. Use your infrastructure's secret store (e.g. Docker secrets, HashiCorp Vault,
+> Ansible Vault, 1Password CLI) and inject variables at deploy time.
+
+### Persistent Data Volume
+
+Mailship stores its data in a **SQLite database** located at `$DATA_DIR/mailship.db`
+(`/data/mailship.db` by default in the Docker image).
+
+- **The database is the single source of truth** for subscriptions, events, and
+  delivery state. Losing it means losing all subscriptions and digest history.
+- **Backup regularly** — a simple `sqlite3 /data/mailship.db .dump` or file-level
+  copy (while the service is idle) is sufficient. For zero-downtime backups, use
+  SQLite's `.backup` command or VACUUM INTO.
+- **Do not share the volume** across multiple Mailship instances — the in-process
+  cron scheduler assumes a single writer.
+- **Volume location** when using Docker Compose:
+
+```sh
+docker volume inspect mailship_mailship-data   # inspect mount point
+docker run --rm -v mailship_mailship-data:/data alpine ls -la /data  # browse contents
+```
+
+To migrate or snapshot, stop the container and copy the database file:
+
+```sh
+docker compose down
+docker run --rm -v mailship_mailship-data:/data -v $(pwd):/backup alpine cp /data/mailship.db /backup/mailship-$(date +%F).db
+docker compose up -d
+```