Switch the subscribe endpoint from POST to an idempotent PUT so clients can
always upsert without a stateful lookup first.
- Add GET /subscription/email?pubkey= lookup so clients can avoid re-POSTing.
- insertSubscription no longer clears confirmed_at unless the email address
changes; a frequency change keeps the existing confirmation.
- registerSubscription only sends a confirmation email when the subscription
is new, unconfirmed, or the email address changed.
- Update integration test and README for the PUT endpoint.
Multi-stage Dockerfile:
- Stage 1: install deps, build TS, build web UI
- Stage 2: minimal production image with sqlite, only prod deps
- Exposes port 4738, uses /data volume for SQLite
docker-compose.yml for easy local deployment with .env support.
.dockerignore to keep the build context lean.
README updated with Docker usage.
.env.template adds DATA_DIR.
