Rewrite appview from Rust to Elixir/Phoenix with PostgreSQL [CL-290]
Read-only Jetstream indexer + query API for encrypted sharing metadata.
Supervision tree: Repo, KeyCache (GenServer+ETS), Endpoint, Consumer (WebSockex).
Three tables (cursor, grants, keyring_members), three API endpoints
(health, inbox, keyrings), Ed25519 auth via Erlang :crypto, Hammer rate
limiting. Includes Dockerfile with auto-migrate entrypoint, docker-compose
for dev, and 37 tests.