Remove the browser admin SPA under web/ that let users log in via
a Nostr signer and manage subscription filters. The server is now
a headless API only.
Changes:
- Delete web/ directory entirely (SPA source, config, deps)
- Remove express.static('web/dist') serving from server.ts
- Simplify GET / handler to always return JSON (no fallback)
- Remove build:web from package.json build pipeline
- Remove web build steps from Dockerfile
- Remove web references from build-in-production.sh
Kept: core subscription/unsubscribe/confirm/notify backend and
transactional src/pages/*.html (part of email flow, not the UI).
75f5908039